Strampop is a subgenre of Alternative Rock. Criteria for a band or musical ensemble to fall under the category of strampop includes roots in rock and pop, but with a tendency to stray radically from the beaten paths.
Strampop is based greatly on differing concepts, rather than the differing styles that these tend to develop, hence inkeeping with the alternative rock trend of classifying a band not by its music, but rather by its method. Hence, one sees bands employing weird chord progressions and eerie sounds, which reflect not only the styles of the band, but also the method by which the musicians arrived at the final destination that is the song.
Hmmm, that new hit by Weezer is an exemplary form of strampop: I think we should write about it on wikipedia...