'Brier root' definitions:

Definition of 'Brier root'

From: GCIDE

Brier \Bri"er\, Briar \Bri"ar\ (br[imac]"[~e]r), n. [OE. brere, brer, AS. br[=e]r, br[ae]r; cf. Ir. briar prickle, thorn, brier, pin, Gael. preas bush, brier, W. prys, prysg.]
1. A plant with a slender woody stem bearing stout prickles; especially, species of Rosa, Rubus, and Smilax. [1913 Webster]
2. Fig.: Anything sharp or unpleasant to the feelings. [1913 Webster]
The thorns and briers of reproof. --Cowper. [1913 Webster]
Brier root, the root of the southern Smilax laurifolia and Smilax Walteri; -- used for tobacco pipes. See also 2nd brier.
Cat brier, Green brier, several species of Smilax (Smilax rotundifolia, etc.)
Sweet brier (Rosa rubiginosa). See Sweetbrier.
Yellow brier, the Rosa Eglantina. [1913 Webster]