A plebe was a newly entered cadet at Starfleet Academy.
Finnegan tormented James T. Kirk while they were at the Academy together, at which time Kirk was a plebe whereas Finnegan was an upperclassman.
Fifteen years later, in 2267, a robot duplicate of Finnegan on the Shore Leave Planet responded to a question Kirk asked him by commenting, "I never answer questions from plebes, Jimmy boy." Kirk replied that he wasn't a plebe. (TOS: "Shore Leave")
In the first draft script of DS9: "In the Pale Moonlight", Jadzia Dax told Captain Benjamin Sisko that she had been a plebe when Leslie Wong had been an instructor at the Academy. However, in the final version of the episode, this reference to "plebe" was instead changed to refer to Dax having been a sophomore. [1]