"горько" meaning in Vieux slave

{
  "categories": [
    {
      "kind": "other",
      "name": "Adverbes en vieux slave",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Vieux slave",
      "orig": "vieux slave",
      "parents": [],
      "source": "w"
    }
  ],
  "etymology_texts": [
    "Adverbialisation en -о de горькъ."
  ],
  "lang": "Vieux slave",
  "lang_code": "cu",
  "pos": "adv",
  "pos_title": "Adverbe",
  "related": [
    {
      "word": "горѥсть"
    }
  ],
  "senses": [
    {
      "glosses": [
        "Amèrement."
      ],
      "id": "fr-горько-cu-adv-GLb~Ndnl"
    }
  ],
  "synonyms": [
    {
      "word": "горьцѣ"
    }
  ],
  "word": "горько"
}

{
  "categories": [
    "Adverbes en vieux slave",
    "vieux slave"
  ],
  "etymology_texts": [
    "Adverbialisation en -о de горькъ."
  ],
  "lang": "Vieux slave",
  "lang_code": "cu",
  "pos": "adv",
  "pos_title": "Adverbe",
  "related": [
    {
      "word": "горѥсть"
    }
  ],
  "senses": [
    {
      "glosses": [
        "Amèrement."
      ]
    }
  ],
  "synonyms": [
    {
      "word": "горьцѣ"
    }
  ],
  "word": "горько"
}