Expressions (phrases, clauses, etc.), Godan verb with 'su' ending
to reveal one's true nature; to show one's true colours; to give oneself away; to be exposed (of a lie, etc.)
Idiomatic expression
彼もついに馬脚を露わした。He has finally shown his true colors.
Also written 馬脚を表す【ばきゃくをあらわす】、馬脚を露わす【ばきゃくをあらわす】