When one wears no underwear beneath his trousers
e.g Did you see Steves arse, he was free balling so hard.

Or, In the sport of cricket one is said to "free ball" when they wear no box (protects genitals) whilst batting.

a Male individual who wears no underwear

n & v. The state of having less restriction over male genitals. - To let testicles hang free.

The art of letting the boys run free, specifically the absence of supportive underpants.

Exhibitionists practice within some groups wherein one does not wear underwear in conjunction with thin fabric or very short short shorts, allowing ones penis and testicles to be viewed by others as they sit or walk about. Provides cheap thrills for both the exhibitionist and voyeur.

Another word could be 'Dangling', because only men can dangle freely.

the act of using your iphone without a case. the term freeballing has meant putting on pants without underwear for years along with "going commando", but in this day and age it's necessary to have a set term for something that people do every day. can be used for non iphones but they are the most fragile phones and will crack easier than others.