wrote:
what's "I high sided" mean.

Never heard that phrase before.

More common in motorcycle riding. The bike slides away from under you
(usually) in a turn, a "low side". If you are really lucky, as the
slide progresses the tyres suddenly gain traction[1]. So, you are
gently moving sideways and all of a sudden the sideways movement stops
and you get 'flicked' over the bike, a "high side".

The sideays movement gets converted into height, and the laws of physics
suddenly look up and demand to know what the hell you are doing up
there. Justice is swiftly dished out, the world carries on knowing that
conservation of energy has not been violated and you add a few civil
engineers to 'Who's going to get it when I go Postal' list.

[1] Usually, but not exclusively, caused by coming off whatever it was
that started the whole shannigans.