Other forms: shams
A sham is something pretending to be what it is not. A complete sham, the whole thing is a sham, a sham marriage.
It is a strong accusation because it says the thing was never real at all: a sham trial, a sham consultation, a sham marriage entered into for a visa — all of these are legal categories as well as insults. As an adjective it means fake: sham indignation. Note shambolic and shameless, which are unrelated; and that a pillow sham is an American term for a decorative cover and is not deceptive at all.
1nounshamSomething pretending to be what it is not.
“The trial was a sham, and everyone knew the verdict before it began.”
2adjectivefakeFake, put on for show.
“She greeted her rival with sham friendliness and a cold smile.”
sham is a pretence.
The word is probably a dialect form of shame, first recorded in the seventeenth century as thieves' cant. Its earliest sense was a trick or hoax, and the meaning of a fake thing followed.
Probably a dialectal form of shame. Alternatively, sham is a term that is used to describe the bottom thick base of a glass, usually a wine or stem glass, where the stem meets the bulbous shape bowl. Glass manufacturers would increase the "sham" to deceive customers into thinking a glass holds more than it actually does. For example, a manufacturer would mold a 12oz glass with a larger "sham" in the base to reduce the volume of the glasses to fit 10-11oz of liquid. By increasing the bulge in the base, usually where the stem meets the glass, it is almost impossible to visually distinguish the difference. This gives the illusion the glass size is the same as any another 12oz glass, but the inside will hold a lesser volume. Later, bringing use to the term "you got shammed" when one party tries to hide something and/or get over on the other party using deceiving tactics.
Etymology from Wiktionary, CC BY-SA