In old texts this character can mean to call out loudly.
Tips
register
Read as 吖 the character means 'to shout / cry out', an archaic usage you'll only see in classical or dialect texts. Modern Chinese uses 喊 or 叫 instead.
The mouth radical 口 appears because the character was coined as a sound-transliteration glyph; the mouth marks it as a phonetic loan rather than a meaning-bearing word.
