A subgroup of a group can also be defined as another abstract group along with an injective homomorphism (or embedding) from that abstract group to the given group. Here, the other abstract group can be naturally identified via its image under the homomorphism, which is the subgroup in a more literal sense.
For the skate brand of the same name, see Roller Derby (brand). Roller derby is a contact sport played by two teams of five members roller skating in the same direction around a track. Game play consists of a series of short match ups (jams) in which both teams designate a jammer who scores points by lapping members of the opposing team.
Kingda Ka is the fastest roller coaster in the United States. It was the fastest coaster in the world for a few years but has since been eclipsed. (It is still the tallest, however.) It's similar to Top Thrill Dragster (although faster), but it feels rougher. If speed is what you are after, Kingda Ka delivers.