A Rossism is an error in speech in which a figure of speech or sentence is jumbled or confused, yet still intelligible.
It was named after Ross O'Donovan, part of the Let's Play duo Steam Train, which is a spin-off of another Let's Play series called Game Grumps. Ross is well-known for accidentally jumbling up locutions.
Some examples for Rossisms:
"That train has sailed."
"It's like listening to a mirror."
"Don't count your chickens before they egg"
"How you going?"
"is rly good"
A Street Rossi is a motorcycle rider driving on public roads who has succumbed to the delusion of thinking he/she has the riding abilities of Valentino Rossi. In the wild, they can be found on public roads riding at 110 mph in a 35, performing aggressive 3-lane changes with no blinker (and cutting off a cager in the process), or - most likely - on the ground in the middle of the road with their bike in 100 pieces. While this person may be mistaken for a squid, they actually have a higher chance of wearing a helmet, due to their desire to look like a racer. The helmet likely sports a highlighter-yellow color along with Monster logo stickers, racing stripes, or triangles like Valentino Rossi'shelmet.
"The Street Rossi stickers are in!! Guys I'm so f**king excited about these I had to slap one on my helmet." - Yammie Noob (a.k.a. Proud Street Rossi)
"A Street Rossi blew past me doing 100 on Main Street today. I caught up with him, though. He was stuck head-first in the window of the 7-11."