Definition of "subliminal"

(physiology) Of a stimulus: below the limen or threshold of conscious perception, especially if still able to produce a response; also (generally), below the threshold where a response can be produced.

(psychology) Without directed awareness or thought; subconscious (dated), unconscious.

(by extension) Of an advertisement, a message, etc.: conveyed in a manner that a person is unaware of being influenced by it.  examples

(physiology) Chiefly preceded by the: something which is below the limen or threshold of conscious perception.

(psychology) Chiefly preceded by the: the subconscious (dated) or unconscious self.

(by extension) An advertisement, a message, etc., which is conveyed in a manner that a person is unaware of being influenced by it.  examples