A loser dweeb is the combination of two devastating insults combined into one powerhouse of an insult. To break it down for you:
loser- someone who just isn't cool and seems to fail at everything
dweeb- someone who is inept at most things, especially around other people
Typically calling someone a loser dweeb should be reserved for only the most catastrophic of blows, they are also generally Welsh.
'Ayo Kai take your dick out that sheep and come play roblox you loser dweeb'
When a slower vehicle overtakes a faster vehicle after a speed contest. After the speed contest has finished, the slower vehicle proceeds to pass the faster vehicle to inflate the ego /recieve an erection/brag to friends, or any combination of the above. This loser flyby can be performed by any make/model of vehicle, as long as the said car is significantly slower than the opponent. See also ricer flyby, meathead flyby.
Billy-boy: Did you see that joe-bob, I just smoked that riceboy civic there?
Joe-bob: No you did'nt, you just performed a loser flyby.
or
Riceboy: Bro I just dusted that Mustang...
Riceboy's friend: Dude...that was a total loser flyby.
That layer of stinky filth that clings to people who have been smoking. This labels them as losers to anyone with a sense of smell. Loserdust also accumulates on the furniture in smoky bars and in the homes of losers.
WOW! That loser upwind of us is not smoking right now, but he is clearly covered with enough loser dust to stink up the whole block! You can even see the shitstain on his mustache from here!