The Rice University Neologisms Database

+1

1. interjection; compounding
   Used in responses or follow-ups in online forums to indicate agreement on a comment or on the original post itself. It more precisely means “my thoughts exactly” or “I agree completely” in reference to the post or comment that it is in response to. Recently, this phrase has transcended the online realm and entered into everyday speech, with some youth animatedly saying the words “plus one” (+1) to indicate their agreement on a matter.
    

   The term +1 was likely coined as a way to quickly indicate your complete and total agreement on a certain matter. Since it’s only two characters long, it definitely saves users time when typing. Furthermore, the +1 concept might have come from some forums that already support some sort of +1 voting button that users can just press to indicate their agreement. For forums that don’t provide this functionality, users likely felt that commenting +1 would have the same effect. Over time, this compound word has transcended internet usage and trickled its way into everyday speech.

   Etymology : Compound of the words plus and one (albeit in symbol form). Plus is its own root, coming from Latin plus, meaning “in greater number,” and one comes from Old English an, meaning “one.”
   Source : Friend 1: “This homework is way too hard. I’m so tired of school.” Friend 2: “+1! +1!” (In person. 10-24-2019)
2. compounding; verb
   To express agreement on an online forum by leaving a “+1” comment. To verbally express agreement by stating the words “plus one.”
    

   See above

   Etymology : See above
   Source : Friend: “I just posted on Piazza. +1 me, I need support.” Me: “Don’t worry, I just +1’d you.” (Through text. 11-25-2019)