stag-horn noun. ['staghɔ:n] Also staghorn, stag's horn. E17.
[from STAG noun + HORN noun.]
1. The antlers of a stag (usu. in pl.); this as a material used to make knife-handles, snuffboxes, etc. E17.

2. a. More fully stag-horn sumac. A N. American sumac, Rhus hirta, with stout upright densely hairy branches forming a flat head, freq. grown for ornament. M18.
b. More fully stag-horn moss, stag's-horn moss, stag's-horn clubmoss. The clubmoss Lycopodium clavatum, so called from its paired terminal spikes, used in homoeopathic remedies. M18.
c. More fully stag-horn fern. Any of various tropical ferns constituting the genus Platycerium, having fertile fronds divided like a stag's antlers. L19.

3. Nautical (staghorn). A bollard with two horizontal arms of the same strength as the upright. E20.

Comb.:
stag-horn calculus Medicine a large stone in the kidney, having the branched form of the renal pelvis that it occupies; stag-horn coral a branching stony coral of the genus Acropora; stag-horn fern: see sense 2c above; stag-horn moss, stag's horn moss, stag's horn clubmoss: see sense 2b above; stag-horn sumac: see sense 2a above.

■ stag-horned adjective that has parts which resemble the antlers of a stag; stag-headed: M19.

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