肚明 [---------]

Jyutping gai1 sik6 fong3 gwong1 cung4 — — sam1 zi1 tou5 ming4
Pinyin jī shí fàng guāng chóng —— xīn zhī dù míng

Definitions (Wiktionary)
  1. phrase, Cantonese, idiomatic
    to be well aware