Real Dictionary

beep
countable noun: A beep is a short, loud sound like that made by a car horn or an answering machine.
verb: If something such as a horn beeps, or you beep it, it makes a short, harsh sound.

beep in American English
the brief, high-pitched sound of a horn, as on an automobile or bicycle
to cause to make such a sound
to make such a sound
intransitive verb: to make or emit such a sound
noun: a short, relatively high-pitched tone produced by a horn, electronic device, or the like as a signal, summons, or warning
transitive verb: to sound (a horn, warning signal, etc.)

beep in British English
noun: a short high-pitched sound, esp one made by the horn of a car, bicycle, etc, or by electronic apparatus
verb: to make or cause to make such a noise