prick up (one's) ears
To suddenly pay close attention to something. Be sure to prick up your ears if anything about the case is mentioned. I can't help but prick up my ears if I hear someone say my name—even if they aren't talking about me.
prick up (one's) ears
To listen with attentive interest.
prick up one's ears, to
To listen attentively. This term, which alludes to horses holding up their ears at a sudden noise, dates from the sixteenth century. Shakespeare used it in The Tempest (4.1): “Like unback’d colts, they prick’d their ears.”