From WordNet (r) 2.0 (August 2003) [wn]:
gander
n : mature male goose
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Gander \Gan"der\, n. [AS. gandra, ganra, akin to Prov. G.
gander, ganter, and E. goose, gannet. See Goose.]
The male of any species of goose.
[1913 Webster]