Subpost
Similar to subtweet but done on Facebook to talk about a Facebook friend by vague-posting behind his or her back.
I think he subposted about me with his vague status "I KNEW he would be there."
subposting
Subposting is sort of like subtweeting but on any platform of social media. Most people subpost with the intention of secretly talking about or referencing (typically a person) that they are angry or annoyed at without directly naming or tagging said person(s). Sometimes subposting can be in a positive manner but usually not as it is an activity usually used by passive-aggressive people.
I was subposting about Monica on Instagram after she was gossiping about me behind my back.