When you do anything possible to buy an item at it's cheapest price, mostly when you shame someone by showing him the same item on the internet cheaper than his so he can sell it to you even cheaper.
Comes from that band with the dude from Hot Rod (well theyre a group) and they made the song 'jizzed in my pants'. A short form for which can be made is "jimp", with a past tense used as "Jimped"
Example 1:
Friend - "Dude, did u just see that hot pic"
You - "YO i just jimped!"
Example 2:
~Random Girl bends down~
You - (Whisper to friend) "yo, jimped"