投石問路 [－－问－]

Jyutping tau4 sek6 man6 lou6
Pinyin tóu shí wèn lù

Definitions (CC-CEDICT)
  1. lit. to toss a stone to find out what's ahead (idiom)
  2. fig. to test the waters
Definitions (粵典–words.hk)
  1. 動詞
    行動​之前​試探​情況
    to test the waters; literally: to toss a stone to find out what is ahead
Definitions (Wiktionary)
  1. phrase, idiomatic
    to test the waters
Definitions (Kaifangcidian)
  1. （沒有對應漢語詞彙）