Equinecessary is not a commonly used word but it refers to something that is necessary for horses. The IPA transcription for the word is /ˌɛkwəˈnɛsəri/. The 'e' in the first syllable is pronounced like the 'e' in 'pet' and the following 'u' is pronounced like 'oo' in 'boot'. The stress is on the third syllable. The concatenated word 'equine' meaning 'horse' is followed by 'necessary', combining to form a word that signifies something essential for horses.