a colon boulder is a fecal equivalent to a kidney stone. they tend to occur when you hold in a shit for whatever reason and finally go to the bathroom hours later. common on road trips, during busy work days, etc. This is as close to prison rape as the common male will ever get. Colon boulders are not to be taken lightly.
Husband: *dials wife's number*
Wife: Hey hun, what do you need?
Husband: Well, i just had a horriffic bathroom experience...total colon boulder.
Husband: Yes...and i'd like to say, don't even bitch to me about child birth again. that fucker had to weigh 3 lbs, and my ass is way smaller than your vagina.
Wife: I don't know what to say...
Husband: You don't have to say shit, but you owe me anal tonight. *click*
Bob: Hey Chuck? Never hold in your shit the day after we go out for pizza...
Chuck: Oh god, what happened?
Bob: You know the rhino scene in that ace ventura movie? I feel kind of like that fake rhino right now...