Boy

a male child, from birth to full growth, especially one less than 18 years of age.
a young man who lacks maturity, judgment, etc.
Informal. a grown man, especially when referred to familiarly:
He liked to play poker with the boys.
a son:
Sam’s oldest boy is helping him in the business.
a male who is from or native to a given place.
boys, (used with a singular or plural verb)

a range of sizes from 8 to 20 in garments made for boys.
a garment in this size range.
the department or section of a store where these garments are sold.

boys, military personnel, especially combat soldiers:
Support the boys overseas.
Disparaging and Offensive. a term used to refer to or address a man considered by the speaker to be inferior in ethnicity, nationality, or occupational status.
a young male servant; page.
Offensive. (in India, China, Japan, etc.) a native male servant, working as a butler, waiter, houseboy, etc.
Nautical. an apprentice seaman or fisherman.
an exclamation of wonder, approval, etc., or of displeasure or contempt.
Contemporary Examples

Lights, Camera, Cocktails Brody Brown October 21, 2011
The Bizarro World Of Iowa’s GOP Convention Ben Jacobs June 22, 2014
George Zimmerman’s Account of Fight With Trayvon Martin Questioned Allison Samuels March 26, 2012
Ann Romney Soars, Chris Christie Stumbles in Kicking Off the Republican Convention Howard Kurtz August 28, 2012
My Former Life As a Kahanist Posterboy Zack Parker June 16, 2013

Historical Examples

The Coyote James Roberts
The Spenders Harry Leon Wilson
Astounding Stories of Super-Science, October, 1930 Various
Brave and Bold Horatio Alger
Pathfinder Alan Douglas

noun
a male child; lad; youth
a man regarded as immature or inexperienced: he’s just a boy when it comes to dealing with women
See old boy
(informal) a group of men, esp a group of friends
generally (derogatory) (esp in former colonial territories) a Black person or native male servant of any age
(Austral) a jockey or apprentice
short for boyfriend
boys will be boys, youthful indiscretion or exuberance must be expected and tolerated
(informal) jobs for the boys, appointment of one’s supporters to posts, without reference to their qualifications or ability
(Irish, informal) the boy, the right tool for a particular task: that’s the boy to cut it
interjection
an exclamation of surprise, pleasure, contempt, etc: boy, is he going to be sorry!
n.

In Old English, only the proper name Boia has been recorded. ME boi meant ‘churl, servant’ and (rarely) ‘devil.’ In texts, the meaning ‘male child’ does not antedate 1400. ModE boy looks like a semantic blend of an onomatopoeic word for an evil spirit (*boi) and a baby word for ‘brother’ (*bo). [Liberman]

A noticable number of the modern words for ‘boy’, ‘girl’, and ‘child’ were originally colloquial nicknames, derogatory or whimsical, in part endearing, and finally commonplace. These, as is natural, are of the most diverse, and in part obscure, origin. [Buck]

Used slightingly of young men in Middle English; meaning “male negro slave or Asian personal servant of any age” attested from c.1600. Exclamation oh, boy attested from 1892.
In addition to the idiom beginning with
boys