Bug  —n. 1 a any of various insects with mouthparts modified for piercing and sucking. B esp. Us small insect. 2 slang virus; infection. 3 slang concealed microphone. 4 slang error in a computer program or system etc. 5 slang obsession, enthusiasm, etc. —v. (-gg-) 1 slang conceal a microphone in. 2 slang annoy. [origin unknown]