A rusty soup can is when two females take an old rusty soup can, which a homeless man has already deficated in after finishing off the remaining contains (prefferably found in a dumpster or other garbage type can or bag), and shove it in both of their asses at the same time. Some performers of the rusty soup can like to take turns inserting the can one at a time.
The homeless guy really liked to watch that rusty soup can, he even performed a nate at the end just to top it off." "My friends did the rusty soup can one time, Dan and Joseph just haven't been the same since." "We performed the rusty soup can the other night, my ass was really burning this morning.