To go without underwear. Sometimes referred to as commando (female) or free-balling (male) in the United States. In fact, it is the way that Scots wearing kilts are supposed to be dressed, unless engaged in some sporting games (ie. Highland games) that my result in their testicles or penis coming into view.
"If that Scot is wearing a kilt at his wedding, he is most certainly regimental."
In exercises, it'd be like going through a regimen of situps, then followed by push-ups, followed by stretches, and then maybe situps again.
All systematic, all pre-planned.
Discriminating and having prejudice of a military regiment; implying some are superior and that others are inferior (unfairly), as well as giving unequal rights to each regiment.
"The 2nd Regiment of Foot Guards were being treated with regimentism, after the were given a unfair position in the Foot Guards precedence list."