I heard a few times the use of the suffix -issimo/issima with substantives and couldn't find an immediate appropriate translation, so I thought it must be metaphorical way of speaking. I don't remember many examples, but recently I stumbled upon the in gambissima expression. Is it grammatically correct to attach the suffix to substantives in some cases? Are there any other examples of this practice?
In the past we had il campionissimo, that is, Fausto Coppi. He was so good in cycling that calling him campione was too reductive. Probably the term was coined under the influence of il generalissimo Franco (taken from Spanish, of course).
Such a usage of the superlative with nouns rather than adjectives has its roots in sport journalism, where people is often in search for astonishing words.
The phrase in gambissima is a joke for saying that someone is in gamba, that is, in good health (or, by extension, good in something) at a very high grade. So it is the superlative of an an adverb, which is not so uncommon, actually, for instance benissimo and malissimo.
Thus sta benissimo can become è in gambissima.