A confusing term. It literally means a condition of ‘equal hand’ (ambit) dexterity or skill across a range of tasks. For tasks requiring little if any skill (e.g., scratching one’s nose), virtually all adults are ambidextrous. For certain skilled tasks, even writing, many adults, with sufficient practice, might be able to achieve ambidexterity or near ambidexterity. When individuals call themselves ambidextrous, they often are referring to this narrowly-focused skill. However, by ambidexterity, they may mean that they preferentially use (and presumably are more skilled with) one hand on some tasks, their other hand on other tasks. The latter condition is more accurately described as ‘mixed’, ‘inconsistent, or ‘weak left- or right-handedness’. By any of these loose usages, ambidexterity would be fairly common in the population. In its strict and literal sense, however, it is extremely rare.
See Bimanual task, Finger-tapping task, Handedness (bimanual and unimanual), Hand preference, Hand proficiency, Handedness (general), Lateral bias, Laterality, Peg-moving task, Unimanual task