A musical subgenre more commonly described without the slash, i.e., "celtic rock." If you like bagpipes, then you just might like them in combination with driving electric guitars and bass. (Though, of course, bagpipes are optional.) Celtic music purists, however, hear it and cringe.
Seven Nations is probably the best-known band in this genre. There are many others who move in and out of "rock" territory while also playing more traditional celtic-folk music (such as Clandestine).
/msg me if you'd like to add to this list, or if you don't think one of them belongs: