Best Answer: perpendicular to the direction of wave motion
think of you and a friend holding different ends of a rope. you shake your end side to side and the wave travels down to your friend's end. if you pay attention to a given segment of the rope, it moves, but it moves to the right and left while the wave travels forward. in a transverse wave, the constituents of the wave move perpendicular to the direction of motion of the wave itself.
a longitudinal wave, on the other hand, is the opposite. the constituents of the wave alternate moving in the same or opposite direction as the wave moves. this one is more like if you and your friend were holding onto a slinky. you give your end a push towards your friend, and you can see the wave move towards the other end.
hope that helps :D