Definition of informal:
boot-cut, composed, familiar, vernacular, articulate, free-and-easy, open, internal, folksy, clingy, unceremonial, chatty, confabulatory, on the loose, by invitation (only), governing, cosy, baggy, congenial, irregular, nonchalant, homey, conversational, ceremonial, structured, idle, restrained, workaday, button-down, common, declamatory, unconventional, self-regulatory, easygoing, versed, crisp, casual, light, triumphal, black-tie, knowledgeable, extempore, bacchanalian, dressy, words, best, escaped, at ease, backless, free, natural, regulatory, plain, cool, motley, economical, brief, spontaneous, discursive, everyday, mixed, at one with, epistolatory, diffuse, BYOB, tiered, sexual, wanton, lax, loose, button-through, tighten, calm, unrestrained, friendly, vulgar, snug, spontaneous, established, sluttish, formal, slack, unorthodox, habitual, subliterary, central, chilled, the more the merrier, unrestrained, heterodox, unceremonious, unofficial, promiscuous, easygoing, laid-back, natural, unstudied, epistolary, unliterary, intimate, nonformal, unaffixed, inner, white-tie, easy, liberal, nonliterary, at large, cozy, unbookish, flat, slangy, unconstrained, exclusive, clean, A-line, colloquial, relaxed, circuitous, structural, relaxed, democratic.
- colloquial (part of speech: adjective)
- succinct (part of speech: adjective)
- "Impressions of South Africa", James Bryce.
- "The Devil's Paw", E. Phillips Oppenheim.
- "A Rogue by Compulsion", Victor Bridges.