It's a blowjob, but not just any typical blowjob. The main difference is that the blowjob is given by two people instead of just one. The two people acts like the two slices of bread while the reciever's cock is like the meat sandwiched between the two slices of bread. Thus, the name "cockmeat sandwich" and always involve at least 3 people.
From 2008 movie
Harold & Kumar Escape from Guantanamo Bay.
This term was used when Big Bob (a guard in Guantanamo Bay) asked Harold & Kumar to get hungry real fast and eat his cockmeat sandwich with extra mayo.
A condesending little cock-sucking douchebag in pastry school. He thinks his cakes are awesome but in reality he is amazingly awful. Likes to pick fights with two of the most badass bitches ever because he is jealous that he cannot be as baller as they are.
Oh, and his breath smells like he just had a cockmeat sammich for lunch.
1) He is such a cockmeat breath, did you see the cake he made?
2) Did you see what happened to cockmeat breath's sugar centerpiece? damnthing was ashamed and jumped right off the table!