Of or describing a lyrical diss whose target or meaning is not explicit. Often used as a noun. See also "Subliminal shot."
Gotta keep your mouth closed or I'ma blast the Mac
They won't believe you, the whole world know that bastard rap
Once you outta the throne you can't have it back
Retirement home and ain't nothing after that
Except you layin in a casket,
Black suit on,
You can't go to heaven with Timberland boots on
No subliminals I ain't talkin to you Shawn
I'm talkin to that heartless mouse with no jewels on -- The Game (200 Bars and Running) 
Here, The Game is dissing Joe Budden (whose old nickname is "Mouse") without mentioning his name. Because he made reference to "the throne" and retirement, The Game found it prudent to explicitly address retired rapper and self-proclaimed "best rapper alive" Jay-Z (Shawn Carter) and tell him that he's not taking subliminal shots at him, but rather at Joe Budden.