Opposite of periodic (see WFTD Period). Something that happens at irregular intervals. An aperiodic waveform in audio is non-repetitive and, consequently, does not have a definite pitch.
“I can talk to my Sales Engineer about any piece of equipment, and he always steers me in the right direction. He truly knows what he's talking about, and he never tries to over-sell me on anything. If he worked in the Nashville area, I'd probably owe him about 20 dinners by now!” Michael Erin Woody, Brentwood, TN