expression, noun-modifying (irregular)
little more than; only slightly better than; almost the same as
Used in the pattern 〜に毛が生えた（ような） to belittle something as being barely an improvement over the base. Often carries a dismissive or humorous tone.
His cooking is little more than an amateur's.
This app has only features that are barely better than the free version.
Literally 'hair has grown', suggesting that adding a little hair to something does not change its fundamental nature. The exact origin is uncertain, but it is a common idiomatic expression.