What term describes a small, random, irregular twitch in a muscle?

The term that describes a small, random, irregular twitch in a muscle is "fasciculation." Fasciculations are involuntary contractions or twitching of small groups of muscle fibers, often visible under the skin. They are typically benign and can occur at rest or during contraction, not indicating any underlying serious condition.

Fibrillation, on the other hand, refers to finer and more rapid contractions that can happen within individual muscle fibers, typically not visible but occurring at a microscopic level. Tremors are rhythmic oscillatory movements often associated with certain medical conditions, typically involving larger groups of muscles. Contracture refers to a condition where a muscle or tendon shortens, leading to a limited range of motion, which is different from the involuntary twitch described by fasciculation.

Thus, "fasciculation" is the appropriate term for the described phenomenon of small, random, irregular twitches in muscles.