"15M" meaning in Spanish

{
  "etymology_text": "Date on which the demonstrations began, 15 May 2011.",
  "head_templates": [
    {
      "args": {
        "1": "es",
        "2": "proper nouns",
        "g": "m",
        "g2": "",
        "g3": "",
        "head": ""
      },
      "expansion": "15M m",
      "name": "head"
    },
    {
      "args": {
        "1": "m"
      },
      "expansion": "15M m",
      "name": "es-proper noun"
    }
  ],
  "lang": "Spanish",
  "lang_code": "es",
  "pos": "name",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Peninsular Spanish",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Spanish entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Spanish numeronyms",
          "parents": [],
          "source": "w"
        }
      ],
      "examples": [
        {
          "english": "\"Here is the precarious youth,\" they introduced themselves. A month later, the 15-M movement was born. It emerged with such force and arrived so silent that it stunned a country with little love for street protest.",
          "ref": "2019 December 16, Inés Santaeulalia, “El asalto al poder de la generación del 15-M”, in El País, Madrid, →ISSN:",
          "text": "“Aquí está la juventud precaria”, se presentaron. Un mes después nacía el 15-M. Surgió con tanta fuerza y llegó tan en silencio que dejó atónito a un país con poca querencia a la protesta callejera.",
          "type": "quote"
        }
      ],
      "glosses": [
        "the Anti-austerity movement in Spain; a series of protests, demonstrations, and occupations against austerity policies in Spain that began around the local and regional elections of 2011 and 2012"
      ],
      "id": "en-15M-es-name-FV0K0pie",
      "raw_glosses": [
        "(numeronym, Spain) the Anti-austerity movement in Spain; a series of protests, demonstrations, and occupations against austerity policies in Spain that began around the local and regional elections of 2011 and 2012"
      ],
      "related": [
        {
          "word": "indignado"
        }
      ],
      "synonyms": [
        {
          "word": "15-M"
        }
      ],
      "tags": [
        "Spain",
        "masculine"
      ]
    }
  ],
  "word": "15M"
}

{
  "etymology_text": "Date on which the demonstrations began, 15 May 2011.",
  "head_templates": [
    {
      "args": {
        "1": "es",
        "2": "proper nouns",
        "g": "m",
        "g2": "",
        "g3": "",
        "head": ""
      },
      "expansion": "15M m",
      "name": "head"
    },
    {
      "args": {
        "1": "m"
      },
      "expansion": "15M m",
      "name": "es-proper noun"
    }
  ],
  "lang": "Spanish",
  "lang_code": "es",
  "pos": "name",
  "related": [
    {
      "word": "indignado"
    }
  ],
  "senses": [
    {
      "categories": [
        "Pages with 1 entry",
        "Pages with entries",
        "Peninsular Spanish",
        "Spanish entries with incorrect language header",
        "Spanish lemmas",
        "Spanish masculine nouns",
        "Spanish numeronyms",
        "Spanish proper nouns",
        "Spanish terms spelled with numbers",
        "Spanish terms with quotations"
      ],
      "examples": [
        {
          "english": "\"Here is the precarious youth,\" they introduced themselves. A month later, the 15-M movement was born. It emerged with such force and arrived so silent that it stunned a country with little love for street protest.",
          "ref": "2019 December 16, Inés Santaeulalia, “El asalto al poder de la generación del 15-M”, in El País, Madrid, →ISSN:",
          "text": "“Aquí está la juventud precaria”, se presentaron. Un mes después nacía el 15-M. Surgió con tanta fuerza y llegó tan en silencio que dejó atónito a un país con poca querencia a la protesta callejera.",
          "type": "quote"
        }
      ],
      "glosses": [
        "the Anti-austerity movement in Spain; a series of protests, demonstrations, and occupations against austerity policies in Spain that began around the local and regional elections of 2011 and 2012"
      ],
      "raw_glosses": [
        "(numeronym, Spain) the Anti-austerity movement in Spain; a series of protests, demonstrations, and occupations against austerity policies in Spain that began around the local and regional elections of 2011 and 2012"
      ],
      "tags": [
        "Spain",
        "masculine"
      ]
    }
  ],
  "synonyms": [
    {
      "word": "15-M"
    }
  ],
  "word": "15M"
}

{
  "called_from": "form_descriptions/1831",
  "msg": "unrecognized sense qualifier: numeronym, Spain",
  "path": [
    "15M"
  ],
  "section": "Spanish",
  "subsection": "proper noun",
  "title": "15M",
  "trace": ""
}

{
  "called_from": "form_descriptions/1831",
  "msg": "unrecognized sense qualifier: numeronym, Spain",
  "path": [
    "15M"
  ],
  "section": "Spanish",
  "subsection": "proper noun",
  "title": "15M",
  "trace": ""
}