adj. Not as happy as one ought or would like to be.
2014
Many Singaporeans are "under happy" at work, or so says a recently released survey. The people behind it coined the phrase "under happy" to describe an in-between state between being happy and unhappy. … Might being under happy be worse than being unhappy, since misery might spur a person to change where mere dissatisfaction does not?
2011
"There's no provision for a federal Department of Happiness, no provision for happiness stamps for the under-happy," Gingrich said. "There's no inherent right to sue if you're unhappy. And the Founding Fathers would have thought that a politician who walked into this room and announced, 'I am now going to take from the overly happy in this end … to redistribute to the under-happy on this side,' was [committing] an act of arrogance worthy of King George."
2005 (earliest)
A slacker wife has the wisdom to accept the following: that a little dirt on her kitchen floor doesn't hurt anyone, that wrinkles on her husband's shirt and on her face are perfectly natural and not worth worrying about, that party guests can be just as happy with a bowl of chips as an elaborate salmon mousse, and that over-scheduled equals under-happy.