Audio: beat (0:04)
beat plays eight beats on a low conga. The beat figure shows the waveform.
A beat is an audible, discrete, repetitive, unpitched sound.
A beat is audible sound, it can be heard. This is the definition of a beat in music. In other contexts a beat is something that is felt rather than heard, such as a heart beat.
A beat is a discrete sound and not a continuous sound. This is one feature that distinguishes rhythm from sound in general. Sound can be continuous or discrete; rhythm is always discrete. Continuous sound does not, and cannot, have a rhythm. In order for a rhythm to exist, there must be a discrete element of some sort in a sound, and that discrete element is what we call a beat.
A beat repeats itself. Repetitive beats make a rhythm.
A beat is unpitched sound. It cannot be notated in staff notation, only in drum notation or waveform notation.