noun U.S. Navy, Marines.
a camp for training recruits.
Origin of boot camp
An Americanism dating back to 1940–45
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
US slang a basic training camp for new recruits to the US Navy or Marine Corps
a centre for juvenile offenders, with a strict disciplinary regime, hard physical exercise, and community labour programmes
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
by 1941, U.S. Marines slang, said to be from boot (n.) as slang for "recruit," which supposedly dates from the Spanish-American War and is a synecdoche from boots, leggings worn by U.S. sailors.
Online Etymology Dictionary, © 2010 Douglas Harper