To Shout, To Scream
intransitive verb, godan verb
This word consists of kanji with hiragana attached. Because the hiragana ends with an う sound, you know this word is a verb. The kanji itself means scream, so the verb version is to scream or to shout.
わめく
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you: If you want to shout at someone you should pick a word that will really hit them. Give them a big whammy (わめ) to the face! Hey, that word works. Shout WHAMMY!
酔っぱらいが喚いているんだよ。
A drunk guy is shouting.