(law, UK historical, otherwise current) A party bringing a suit in civil law against a defendant; accuser.

(law) A party who appeals the decision of a lower court.

In a plain manner; simply; basically. / Obviously; clearly.

Sounding sorrowful, mournful or melancholic.

(cryptography, computing) Alternative spelling of plain text

(poetic or archaic) A lament or woeful cry. / A complaint. / (archaic) A sad song. / (archaic or UK law) An accusation.

Speaking plainly or simply.

comparative form of plain: more plain

(usually of a police officer) Wearing ordinary civilian clothes instead of a uniform, in order to avoid detection.

Ordinary civilian clothes, rather than uniform.