(countable, uncountable) A muscular organ that pumps blood through the body, traditionally thought to be the seat of emotion.
(uncountable) One's feelings and emotions, especially considered as part of one's character.
(countable, uncountable) The seat of the affections or sensibilities, collectively or separately, as love, hate, joy, grief, courage, etc.; rarely, the seat of the understanding or will; usually in a good sense; personality.
(countable, uncountable) Emotional strength that allows one to continue in difficult situations; courage; spirit; a will to compete.
(countable, uncountable) Vigorous and efficient activity; power of fertile production; condition of the soil, whether good or bad.
(archaic, countable, uncountable) A term of affectionate or kindly and familiar address.
(countable, obsolete, uncountable) Memory.
(countable, figuratively, uncountable) A wight or being.
(countable, uncountable) A conventional shape or symbol used to represent the heart, love, or emotion: ♥.
(countable, uncountable) A playing card of the suit hearts featuring one or more heart-shaped symbols.
(countable, uncountable) The twenty-fourth Lenormand card.
(countable, figuratively, uncountable) The centre, essence, or core.
(countable, figuratively, uncountable) The centre, essence, or core.

(humorous, informal, transitive) To be fond of. Often bracketed or abbreviated with a heart symbol.
(transitive) To mark a comment, post, reply, etc., with the heart symbol (❤).
(obsolete, transitive) To give heart to; to hearten; to encourage.
(transitive) To fill an interior with rubble, as a wall or a breakwater.
(intransitive) To form a dense cluster of leaves, a heart, especially of lettuce or cabbage.