Best definition
An up and down romance. Very rocky and unsteady romance like a yo-yo.

Man, Sydney and Ron’s relationship is a total yomance. This morning they hated each other fighting, now they’re shopping for engagement rings.

Selena and Justin Bieber? Perfect example of a yomance… more on-and-off than anyone.

Nah, we are nothing serious. It’s a yomance, nothing too consistent.

Yomance: define #2
A “friendship” with someone who calls you a good friend, only to pop in and out once in a while and say nothing but a brief “yo”, “hey”, and only talks with you if you talk with them first. Most likely this person has had at one time a special meaning to you.
Ashita and I were such good “friends” it turned into a yomance.

Yomance is another word for a friend who no longer contributes to the relationship and becomes a casual acquaintance.