Ticktock is a commonly used onomatopoeic word that describes the sound made by a clock's pendulum as it swings back and forth. While the word is specific to clock movements, there are many synonyms for it that describe similar sounds. These include words such as "clip-clop," "pitter-patter," "thump-thump," and "ticking." Other synonyms include "heartbeat," "pulse," and "metronome." These words can be used in different ways to describe different situations. For example, "thump-thump" might be used to describe the sound of a heavy heartbeat, while "metronome" might be used to describe the rhythmic ticking of a musical instrument.