informal Definition

informal
adj

1. Without ceremony or formality; relaxed and friendly.

Thesaurus: casual, relaxed, natural, familiar, simple, colloquial, homey, unceremonious, unofficial.
2. Said of language, clothes, etc: suitable for and used in relaxed, everyday situations.
(Austral)
(NZ)
3. Said of a vote, ballot, etc: not valid.

Derivative: informality

Lack of formality.
Thesaurus: casualness, familiarity, ease, congeniality, simplicity, unceremoniousness, unpretentiousness.

An instance of this.

Derivative: informally
adverb

In a relaxed or unceremonious way
Thesaurus: casually, simply, easily, colloquially, unofficially, privately, unceremoniously.

Etymology: 17c.