In a post that would be horribly NSFW were it not all just a block of text, linguist Arnold Zwicky blogs about how the vagaries of English allow you to interpret the same line from a gay porn in multiple ways.
The story begins with a young man crying out, (1) "Oh yeah, shoot my ass!," at the climactic moment of a segment in the gay porn compilation video A Bronco Named Brad (on the video, see here). The speaker is asking his partner to (2) "shoot [your cum] on my ass, ejaculate on my buttocks" [ONTO reading].
In other contexts, (1) could convey (3) "shoot [your cum] in(to) my ass, ejaculate in(to) my anus" [INTO reading]. Note the two different senses of ass here— 'buttocks' or 'anus', with the anus being the centerpiece of the buttocks, so to speak—related metonymically.
But now for the main linguistic point, shoot 'ejaculate' used, exceptionally, as a transitive verb ...
From there, the post rises to a level of technical language analysis that almost, *almost* distracts from the fact that we're talking about the use of language in a porn that seems to be targeted at Brad-fetishists.
Submitterated by Sam