In a manner that is somewhat black or dark in color; to a degree that is somewhat blackish.
Adverbial form created by adding '-ly' to the adjective 'blackish.' However, this word is rare because adverbs describing colors are uncommon in English; we typically don't need to describe how blackly something appears.
'Blackishly' is technically valid English, but you'd almost never hear it used because English speakers don't typically modify color descriptions with adverbs—we say 'it looks blackish' not 'it appears blackishly,' which reveals how grammar rules interact with what sounds natural.
Complete word intelligence in one call. Free tier — 50 lookups/day.