What does "alternative fact" mean?

Something presented as a fact for reasons of political expediency; a fiction, a falsehood, a lie.

Alternative fact

noun

noun ·Rare ·Advanced level

Noun

1
Something presented as a fact for reasons of political expediency; a fiction, a falsehood, a lie.
"They are creating their own facts, but one need not be in Government to create alternative facts."
2
Used other than figuratively or idiomatically: see alternative, fact.
"That Newton was an empirical scientist is a fact. An alternative fact is that he was an alchemist."

"They are creating their own facts, but one need not be in Government to create alternative facts."

This term gained prominence after it was used by Kellyanne Conway in January 2017 and widely repeated in the US media.