(countable, uncountable) A male child.
(countable, uncountable) A young man.
(countable, diminutive, especially, uncountable) A son of any age.
(countable, diminutive, endearing, uncountable) A male human younger than the speaker.
(countable, derogatory, informal, mildly, sometimes, uncountable) A male human of any age, as opposed to a "girl" (female human of any age).
(countable, obsolete, uncountable) A male of low station, (especially as pejorative) a worthless male, a wretch; a mean and dishonest male, a knave.
(countable, uncountable) A male servant, slave, assistant, or employee, particularly
(countable, uncountable) A male servant, slave, assistant, or employee
(countable, historical, offensive, uncountable) A male servant, slave, assistant, or employee
(countable, obsolete, uncountable) A male servant, slave, assistant, or employee
(countable, offensive, uncountable) Any non-white male, regardless of age.
(countable, especially, informal, uncountable) A male friend.
(countable, uncountable) A male submissive.
(countable, uncountable) A male non-human animal, especially, in affectionate address, a male pet, especially a dog.
(countable, historical, uncountable) A former low rank of various armed services; a holder of this rank.
(US, slang, uncountable) Heroin.
(childish, countable, uncountable) A male (tree, gene, etc).
(colloquial, countable, endearing, uncountable) Any tangible object close to one's person; often used in emphatic forms such as bad boy.

Exclamation of surprise, pleasure or longing.

To act as a boy (in allusion to the former practice of boys acting women's parts on the stage).