1.Definition: exceedingly sudden and unexpected

"Came to an abrupt stop", "An abrupt change in the weather"

2.Definition: extremely steep

"An abrupt canyon"

Related Adjective(s):precipitous, sharp

3.Definition: marked by sudden changes in subject and sharp transitions

"Abrupt prose"

Related Adjective(s):disconnected

4.Definition: surprisingly and unceremoniously brusque in manner

"An abrupt reply"