The discrimination or prejudice against people of an "abnormal" body size, whether it's height or weight.
"Look at that girl, she's so fat. How disgusting!"
"Look at that girl, she's so tall. How weird!"
These are examples of sizism.
Discrimination towards people of a different height, usually against people at the extremes of the height range, i.e: Extremely tall people or extremely short people.
Similar to racism but concerning height, not race.
To be sizist is to be discriminatory in relation to height.
Same as sizeism
Jack: I hate that guy, he's freakishly tall!
Jill: Don't be so sizist!
Activist: Sizism is wrong. Height should not be an important factor in judging a person.