"The jock strap. a) What is it? And b) What can it do for you? Arnold!"
"The jock strap, sir, is a particular kind of strap, made out of a strap-like material, used exclusively for the purposes of jocks."
-- Coach Cutlip (Robert Picardo1
Kevin Arnold (Fred Savage), "The Wonder Years", pilot episode
(ABC-TV, US, 1988)
A more common term for an athletic supporter. This term is favored in spoken conversation, whereas "athletic supporter" is favored in print. It's not really slang, in that no one will correct you for using it (as opposed to words like
"ain't" or any number of synonyms for body parts.) But for some reason, there's a common hangup about putting it to paper.
It is meant to be worn by males while playing sports (or any other athletic activity,) in place of undergarments, and holds the genitals
in place. If you search hard enough, you may find explanations that this is
neccessary to prevent strain on the tissues which support the testes, or worse, from having them twist, during vigorous activity which may bounce them about.
But the most common response to the question "why do I have to wear this?"
seems to have long been "because it's required", or "if you don't, the teacher/coach will run your ass2".
Most jock straps have a wide (about three inch) elastic waistband, a pouch (which
holds the unmentionables,) and two thin leg straps that connect the bottom
of the pouch to the side of the waistband. Think "tighty whities with the
back cut out", though the pouch is generally lighter and more airy than
what conventional underwear is made from. This seems to keep things cooler
and better enables perspiration to evaporate. A common variation has an enclosed pouch designed to hold a protective cup, for use in contact sports. Heavily padded versions are made for hockey goalies.
Many pop culture references identify these as mandatory equipment at and above the junior high level of US physical education classes, along with various associated rites of passage such as jock checks, cup checks, and having your jock snapped3 by class/teammates. None of my schools required them. (I don't know if I should feel left out. Probably not.)
In more recent years, its use seems commonly abandoned in favor of compression shorts.
You're probably thinking, "This node has more detail than I wanted to know."
1Yes, Voyager's Emergency Medical Hologram.
2As TheLordScribe so eloquently puts it.
3The male equivalent of girls getting their bra snapped