Source: Word Spy
regift (REE.gift) v. To give as a gift something that one received as a gift.—n.
—regifter n.
Today's word originated with that always reliable source of neologisms, the TV show Seinfeld. Regift (and the noun regifter) appeared in the episode titled The Label Maker, which first aired on January 19, 1995. It took a while, but regift eventually embedded itself in the language. The proof? I found dozens of media citations that used the word without referencing its Seinfeldian origins. That's not surprising since the word fills in a language gap and succinctly describes something that the majority of us have done (see the earliest citation for a stat).
Here's the script snippet where regift was used in that Seinfeld episode (regifter was used earlier in the show; note, as well, yet another neologism: degift):
George: The wedding is off. Now you can go to
the Super Bowl.
Jerry: I can't call Tim Whatley and ask for the
tickets back.
George: You just gave them to him two days ago,
he's gotta give you a grace period.
Jerry: Are you even vaguely familiar with the
concept of giving? There's no grace period.
George: Well, didn't he regift the label maker?
Jerry: Possibly.
George: Well, if he can regift, why can't you
degift?
Jerry: You may have a point.
George: I have a point, I have a point.
No-Regifting!