extra-conjugal
extraconjugal
extracurricular
criminal conversation
adultery
fornication
something-something
extramarriage
mistress
number two
sow one's wild oats
nonmarriageable
free love
extramarital sex
kept woman
hetsex
fancy woman
mistressdom
mated
rumpty-tumpty
jiggy jiggy
sestolet
conjugation
consummation
bonky bonky
throes of passion
dry sex
jigajig
sexual congress
boinky
marital embrace
humpa humpa
act of darkness
intimate relations
in-out
job
connection
pareunia
go to bed with
know someone in the biblical sense
jump someone's bones
two-timing
fornicate
nonincestuous
unincestuous
hexadactylism
sexennary
hexadactyly
heterosex
at it