Webster's Revised Unabridged Dictionary · 1913

Glyn

Glyn , noun

[Obs. singly, but occurring often in locative names in Ireland, as Glen does in Scotland.]

A glen. See Glen. [Obs. singly, but occurring often in locative names in Ireland, as Glen does in Scotland.]
He could not beat out the Irish, yet he did shut them up within those narrow corners and glyns under the mountain's foot. — Spenser

Also: Glynne