A suspended roller coaster is a type of roller coaster where the enclosed train is held underneath the track. Suspended coasters are different from inverted roller coasters because suspended coasters have the ability to swing freely with lateral g-forces. Designers were never able to get suspended coasters to perform loops. They first started out as gondolas hanging from tracks and being carried uphil in the 1900's.
A similar concept is the Wilde Hilde, where the track is vertical and the train is held beside it.