A portmanteau of 'fecal' and 'particulate'.
Feticulate is the collective term for the airborne microscopic shit particles which accompany a fart. The level of feticulate is much worse if the fart is unfiltered (via clothing such as underwear) or if the originator of the fart accidentally draws muck at the time of farting.
"Please keep you anus closed while we are in the elevator. I do not care to breathe your feticulate."