n. The state or quality of being apt or fit for or suited to a purpose, place, or situation; fitness; suitableness.n. A natural tendency or acquired inclination; both capacity and propensity for a certain course: as, oil has an aptitude to burn; men acquire an aptitude to particular vices.n. Readiness in learning; teachableness; quickness to understand and acquire; intelligence; talent.n. Synonyms Faculty, Capacity, etc. See genius.