(intransitive) Often followed by up: to become happy; to brighten up, to cheer up.. (transitive) Often followed by up: to make happy; to brighten, to cheer, to enliven. Preceded by the: happy people as a group. (as a suffix to a noun) Favoring or inclined to use.. (rare) Of persons, especially when referring to their ability to express themselves (often followed by at or in): dexterous, [...]
(intransitive, informal) To celebrate one's birthday. The anniversary of the day on which someone is born. [From 1570s]. The anniversary of the day on which something is created.. The date on which someone is born or something is created, more commonly called birthdate or date of birth.
(colloquial, transitive) To wish (someone) a happy birthday. Said or written to a person who is celebrating his or her birthday in order to convey the good wishes of the speaker or writer (literally, "may you have a happy birthday").