'Onset' definitions:

Definition of 'onset'

From: WordNet
noun
The beginning or early stages; "the onset of pneumonia" [syn: onset, oncoming]
noun
(military) an offensive against an enemy (using weapons); "the attack began at dawn" [syn: attack, onslaught, onset, onrush]

Synonyms of 'onset'

From: Moby Thesaurus

Onset, MA -- U.S. Census Designated Place in Massachusetts

From: Gazetteer 2000
Name :
Onset, MA -- U.S. Census Designated Place in Massachusetts
Population (2000) :
1292
Housing Units (2000) :
910
Land area (2000) :
1.083253 sq. miles (2.805612 sq. km)
Water area (2000) :
0.215025 sq. miles (0.556913 sq. km)
Total area (2000) :
1.298278 sq. miles (3.362525 sq. km)
FIPS code :
51160
Located within :
Massachusetts (MA), FIPS 25
Location :
41.746424 N, 70.663251 W
ZIP Codes (1990) :
02532
Note :
some ZIP codes may be omitted esp. for suburbs.