verb; play with the words. It refers to harshly looking for the mistakes of others, of the words / language used which may be inaccurate, ambiguous or omissions of words; making it difficult for the other person.
Definitions (粵典–words.hk)
動詞
專挑人哋用字嘅錯處，當係蝨噉捉 to find fault with the choice of words; to be fastidious about wording; literally: to pick up a flea from a word
佢個人好鬼衰㗎，專捉人字蝨，次次都窒住晒。
佢个人好鬼衰㗎，专捉人字虱，次次都窒住晒。
keoi5 go3 jan4 hou2 gwai2 seoi1 gaa3, zyun1 zuk1 jan4 zi6 sat1, ci3 ci3 dou1 zat6 zyu6 saai3. He's a very bad guy. He always finds fault with others' choice of words and keeps interrupting.
呢個人淨係識得捉人字蝨，根本俾唔到咩實際建議！
呢个人净系识得捉人字虱，根本俾唔到咩实际建议！
ni1 go3 jan2 zing6 hai6 sik1 dak1 zuk1 jan4 zi6 sat1, gan1 bun2 bei2 m4 dou2 me1 sat6 zai3 gin3 ji5! This guy only focuses on fault with the choice of words, without any practical advice!
參看
捉字虱
Definitions (Wiktionary)
verb, Cantonese
to be picky with words; to pay too much attention to the shades of meanings of words; to find fault with the choice of words (syn.) 摳字眼兒, 抠字眼儿