What does "vanishingly" mean?

So as to vanish, or appear to vanish; especially, very small or rare.

What is a synonym for "vanishingly"?

Common synonyms include: infinitesimally.

adv

adv ·Rare ·Advanced level

Adverb

1
So as to vanish, or appear to vanish; especially, very small or rare. not-comparable
"vanishingly rare"

Adverb

"The probability that it will ever happen is vanishingly small."

From vanishing + -ly.