incontinence
A character loses control of their bladder. This can be the result of sudden and extreme stress, such as being scared shitless, or overstimulated. In some cases, it can be an ongoing issue cased by the nerves that control the bladder.
Note that this is not the same as watersports: this tag doesn't imply that characters are interested in the urine itself in any way.
See also:
death piss - The corpse of a character is shown urinating due to loss of bladder control.
omorashi - A fetish involving people with full bladders either wetting themselves or coming close to it.
peeing - A character is actively urinating.
urine - The urine itself.
urine pool - A puddle of urine.
watersports - Any sexual activity that involves urine and peeing.
wetting - A character urinates into their clothing, usually by accident.