A sudden rush of nostalgia that has been stock-piled for a long time being unleashed. Most of the time it's because of fun stuff you've done in the past and now once again allowed to relive those time, or at least remembering them...
Usually in form of not being able to think straight because of the awesomeness that just happened. A feeling where you just want to smoke a cigar, grab a minigun and drown anything in sight with lead.
This feeling is uncommon, some just get "Nostalgia" but this is in rush form which makes you totally unprepared and you'll be completely overwhelmed by the feeling. Which leaves you there incapacitated thinking about it rather than anything else.
James:*Sees Dave playing Galaga* What's tha- *nostalgia rushes* Wait,wait,wait,wait,wait... o-oh my god, hold on. ohh-hh man Nostalgia Rushing! So much badassery!
Dave:Woah dude you cool?
James: All cool man, just Oh y-Yeahhh... Damn, I feel rejuvinated! Hug me bro! (all homo intended)
Dave: Get the hell off me!! If you're having another Nostalgia Rush I'm outta here!