Alternative dialogues words you could use instead of the the word…

Plain

As an adjective

Specifically meaning honest expression

Abrupt

Artless

Bluff

Blunt

Brusk

Brusque

Candid

Crusty

Curt

Direct

Ernest

Forthcoming

Forthright

Foursquare

Frank

Free hearted

Free spoken

Guileless

Gruff

Honest

Impertinent

Impolite

Inconsiderate

Ingenious

Innocent

Naive

Natural

Open

Openhearted

Out front

Outspoken

Plainspoken

Real

Rude

Sharp

Sincere

Straightforward

Tactless

Unaffected

Uncivil

Indesigning

Undiplomatic

Ungracious

Unguarded

Uninhabited

Unmannerly

Unpretending

Unpretentious

Unreserved

Unrestrained

Unsuitable

Vocal

Vociferous