"μῦ" meaning in Grec ancien

{
  "categories": [
    {
      "kind": "other",
      "name": "Noms communs en grec ancien",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Noms des lettres grecques en grec ancien",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Grec ancien",
      "orig": "grec ancien",
      "parents": [],
      "source": "w"
    }
  ],
  "etymology_texts": [
    "Sonorisation de μ, le français sonorise en èm en antéposant une voyelle."
  ],
  "lang": "Grec ancien",
  "lang_code": "grc",
  "pos": "noun",
  "pos_title": "Nom commun",
  "raw_tags": [
    "μῦ, mû"
  ],
  "related": [
    {
      "word": "μύ"
    }
  ],
  "senses": [
    {
      "glosses": [
        "Mu, la douzième lettre de l’alphabet grec."
      ],
      "id": "fr-μῦ-grc-noun-er8UEDT1"
    },
    {
      "examples": [
        {
          "text": "μῦ λαλεῖν, murmurer."
        }
      ],
      "glosses": [
        "Son indistinct, meuh, murmure."
      ],
      "id": "fr-μῦ-grc-noun--nieOti9"
    }
  ],
  "sounds": [
    {
      "ipa": "*\\ˈmyːˌ\\"
    }
  ],
  "tags": [
    "neuter"
  ],
  "word": "μῦ"
}

{
  "categories": [
    "Noms communs en grec ancien",
    "Noms des lettres grecques en grec ancien",
    "grec ancien"
  ],
  "etymology_texts": [
    "Sonorisation de μ, le français sonorise en èm en antéposant une voyelle."
  ],
  "lang": "Grec ancien",
  "lang_code": "grc",
  "pos": "noun",
  "pos_title": "Nom commun",
  "raw_tags": [
    "μῦ, mû"
  ],
  "related": [
    {
      "word": "μύ"
    }
  ],
  "senses": [
    {
      "glosses": [
        "Mu, la douzième lettre de l’alphabet grec."
      ]
    },
    {
      "examples": [
        {
          "text": "μῦ λαλεῖν, murmurer."
        }
      ],
      "glosses": [
        "Son indistinct, meuh, murmure."
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "*\\ˈmyːˌ\\"
    }
  ],
  "tags": [
    "neuter"
  ],
  "word": "μῦ"
}