expression, i-adjective
next to nothing; essentially nonexistent; virtually nil
Used to emphasize that something is so small, insignificant, or unlikely that it can be treated as nonexistent. Often follows a noun or nominalized phrase.
彼の給料はないに等しい。
His salary is next to nothing.
この町には娯楽施設はないに等しい。
There are virtually no entertainment facilities in this town.
皆無 means 'none at all' or 'completely absent', a stronger and more absolute statement than ないに等しい, which allows for a negligible amount.
ほとんどない is a more common and less formal way to say 'almost none', while ないに等しい is slightly more emphatic and literary.
Phrase composed of ない (nonexistent) + に (particle) + 等しい (equal). Literally 'equal to nonexistent'.