1. (on the Twitter website) a hostile or otherwise negative post that is addressed to or about a particular person but does not mention the person’s username or does not name the person at all.
verb (used with or without object)
  1. to post such a message or tweet about (someone) on Twitter: I wish she’d stop subtweeting and talk to me in person.

Origin of subtweet

2009; sub(liminal) + tweet (in the sense “a message posted on Twitter”)
Related formssub·tweet·er, noun Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018