"F+" meaning in English

{
  "head_templates": [
    {
      "args": {
        "1": "en",
        "2": "noun"
      },
      "expansion": "F+",
      "name": "head"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 2 entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Academic grades",
          "orig": "en:Academic grades",
          "parents": [
            "Education",
            "Society",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "An academic grade given by certain institutions. Slightly better than an F and slightly worse than a D−."
      ],
      "id": "en-F+-en-noun-C7D1SL5t",
      "links": [
        [
          "F",
          "F"
        ],
        [
          "D−",
          "D−"
        ]
      ],
      "related": [
        {
          "word": "E+"
        }
      ]
    }
  ],
  "word": "F+"
}

{
  "head_templates": [
    {
      "args": {
        "1": "en",
        "2": "noun"
      },
      "expansion": "F+",
      "name": "head"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "related": [
    {
      "word": "E+"
    }
  ],
  "senses": [
    {
      "categories": [
        "English entries with incorrect language header",
        "English lemmas",
        "English nouns",
        "English terms spelled with +",
        "Pages with 2 entries",
        "Pages with entries",
        "en:Academic grades"
      ],
      "glosses": [
        "An academic grade given by certain institutions. Slightly better than an F and slightly worse than a D−."
      ],
      "links": [
        [
          "F",
          "F"
        ],
        [
          "D−",
          "D−"
        ]
      ]
    }
  ],
  "word": "F+"
}