for·mal / ˈfôrməl/ • adj. 1. done in accordance with rules of convention or etiquette; suitable for or constituting an official or important situation or occasion: a formal dinner party. ∎ (of a person or their manner) prim or stiff. ∎ of or denoting a style of writing or public speaking characterized by more elaborate grammatical structures and more conservative and technical vocabulary. ∎ (esp. of a house or garden) arranged in a regular, classical, and symmetrical manner.2. officially sanctioned or recognized: a formal complaint. ∎ having a conventionally recognized form, structure, or set of rules: he had little formal education.3. of or concerned with outward form or appearance, esp. as distinct from content or matter: I don't know enough about art to appreciate the purely formal qualities. ∎ having the form or appearance without the spirit: his sacrifice will be more formal than real. ∎ of or relating to linguistic or logical form as opposed to function or meaning.• n. an evening gown. ∎ an occasion on which evening dress is worn.