The disgusting (or highly-amusing, depending on your tastes in humor) act of farting while having missionary-style sex; it occurs when the person who's "on top" breaks wind and thus sends a "strong breeze" of gas whooshing out past the dampened thighs of the person on the bottom. Depending on how hot/chilly said "
blast from the past" happens to be --- and on how temperature-sensitive the other person's upper-leg skin happens to be --- you may receive a howl of protest from said
whizzpopper's "recipient", since many people hate the feel of "drafts" on their
bare legs.
Depending on the condition/behavior of the lovers' digestive systems --- and whether they
partook of baked beans and/or
stewed cabbage shortly beforehand --- one or both of them may have "lots of traffic on the overpass" --- i.e., a frequent explanation of putrid methane while they're lustily "having at it" and thus vigorously flexing their entire groin-area anyway. Extra points if (1) you are able to skillfully "time your
toots" so that they occur at precisely-regular intervals to
coincide with your thrusting "rhythm", and/or (2) on occasions when both of you are passing gas while "getting it on", you practice standard "courtesy-merging on the freeway" --- i.e., you each "take turns" farting so that one of you (usually the guy, since it's easier for him to tense his abdominal muscles during his forward thrust) releases your "perfume" on each "inward" stroke, and the other person "lets fly" on the "outward" motion, so that your "collective" farts are "
synchronized" and evenly
spaced from each other, similar to
two lines of cars alternately merging on adjacent highway-lanes like the opposing teeth of a zipper.