Dictionary.com
definitions

gen.

gender.
general.
genitive.
genus.

Gen.

Military. General.
Genesis.
Geneva.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for gen.

Gen.

abbreviation for

General
Bible Genesis
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012