(Noun) - A highly appealing abdominal region on a woman that causes an extremely strong desire in a man on which to ejaculate sperm.
It is not uncommon during intercourse that a man may achieve orgasm while in the missionary position. If he removes himself from the woman just prior to ejaculation, a frequent and convenient zone of fluid deposit is her abdominal area. A heightened level of satisfaction from performing this act can be attained by the woman having toned abdominal muscles, or at least having the appearance of such. Thus, the woman has a great stomach to cum on, or a "cumach".
Susie has been doing a lot of sit-ups. She has a total cumach now.