From The Collaborative International Dictionary of English v.0.48 :
Sweetbrier \Sweet"bri`er\, n. (Bot.)
A kind of rose ({Rosa rubiginosa) with minutely glandular
and fragrant foliage. The small-flowered sweetbrier is Rosa
micrantha.
[1913 Webster]
From WordNet (r) 3.0 (2006) :
sweetbrier
n 1: Eurasian rose with prickly stems and fragrant leaves and
bright pink flowers followed by scarlet hips [syn:
sweetbrier, sweetbriar, brier, briar, eglantine,
Rosa eglanteria]