1) Catch 2) Catch accidentally 3) Catch this way 4) Do some eavesdropping 5) Eavesdrop 6) Find out by eavesdropping 7) Hear 8) Listen in on, accidentally 9) Make out at a party 10) Pick up by the ears 11) Take in 1) Catch 
• (v. t.) To hear more of (anything) than was intended to be heard; to hear by accident or artifice. • (v. t.) To hear again.
O`ver·hear' transitive verb [ imperfect & past participle Overheard ; present participle & verbal noun Overhearing .] [ Anglo-Saxon oferhiéran .] 1. To hear more of (anything) than was intended to be heard; to hear by acc...
to hear (speech or a speaker) without the speaker's intention or knowledge: I accidentally overheard what they were saying.