Is “Optimum” a Scrabble word?
Yes
OPTIMUM
Valid in at least one Scrabble dictionary
Valid in these dictionaries
SOWPODS / CSW
Scrabble UK & International
TWL / NWL
Scrabble North America
Large English Dictionary
General English word list
Meaning of Optimum
/ˈɒptɪməm/
noun
1.The best or most favorable condition, or the greatest amount or degree possible under specific sets of comparable circumstances.
adjective
1.The best or most advantageous; surpassing all others.
Synonyms: best, ideal, optimal