shamrock Meaning, Definition & Usage

  1. noun creeping European clover having white to pink flowers and bright green leaves; naturalized in United States; widely grown for forage
    white clover; dutch clover; Trifolium repens.
  2. noun Eurasian plant with heart-shaped trifoliate leaves and white purple-veined flowers
    Oxalis acetosella; common wood sorrel; cuckoo bread.
  3. noun clover native to Ireland with yellowish flowers; often considered the true or original shamrock
    Trifolium dubium; lesser yellow trefoil; hop clover.

WordNet

Sham"rock noun
Etymology
L. seamrog, seamar, trefoil, white clover, white honeysuckle; akin to Gael. seamrag.
Definitions
  1. (Bot.) A trifoliate plant used as a national emblem by the Irish. The legend is that St. Patrick once plucked a leaf of it for use in illustrating the doctrine of the trinity. ✍ The original plant was probably a kind of wood sorrel (Oxalis Acetocella); but now the name is given to the white clover (Trifolium repens), and the black medic (Medicago lupulina).

Webster 1913