The ability for an often-times too small t-shirt to be used exclusively as an undershirt, mostly worn under polos. This term refers mostly to preppy teenage males but it can apply to many different male groups.
Walker: Man... I was brushing my hair for the third time this morning and I noticed that this T-shirt is way too small for me now.
Trey: Don't worry, its still totally undershirtable. I've got like a whole closet full of them.
Providing too little information or context when blogging or tweeting. With the ubiquitous status updates on Facebook and Twitter, people forget that it can be helpful to provide enough context for a message to be meaningful. So, ironically, while people tend to overshare, they also undershare at the same time!
Guy 1: I got a tweet last night from Jim, he said, "this is so effing great!"
Girl 1: I saw that, too. Why does he constantly undershare?!
Guy 1: Probably wasn't that great.
The state when one feels less involved in posting stuff on social media than one desires to, frequency-wise or volume-wise, usually in order to overly express one's self or to fulfill a business need, thus experienced by extroverts and business people.
The opposite of overused.
A word that you had in your daily vocabulary but somehow forgot. It might even got overused but because you haven't used it in a long time it got underused again
Guy1: There's a wet t-shirt contest in the hotel.
Guy2: Epic!
Guy1: They're still looking for 3 judges btw.
Guy3: We gotta register as judges.
Guy1: Already done guys, and guess what we were already picked
Guy2&3: Legendary!
Guy1: Guys that's not legendary, that's fucking ZEDERN!
Guy2: God totally forgot zedern, totally underused :P