Is “Onset” a Scrabble word?
Yes
ONSET
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 Onset
/ˈɒnˌsɛt/
noun
1.An attack; an assault especially of an army.
2.The initial phase of a disease or condition, in which symptoms first become apparent.
“the onset of schizophrenia”
3.The initial portion of a syllable, preceding the syllable nucleus.
Synonyms: beginning, start, storming
verb
1.To assault; to set upon.
2.To set about; to begin.