To strike the palms of your hands together sharply to make a sound, usually to show approval; a sudden loud sound.
From Old English 'clappan' meaning 'to knock or strike.' Related to 'clap' the disease (gonorrhea), which came later from the striking pain of the illness. The appreciative hand-clapping sense is oldest.
Applause evolved as a human behavior remarkably recently—ancient Romans didn't clap, they snapped their fingers and made sounds from the stands. Clapping as approval is a medieval European invention that spread globally relatively recently.
Complete word intelligence in one call. Free tier — 50 lookups/day.