The Collaborative International Dictionary of English v.0.48:

Sea holm \Sea" holm`\
   A small uninhabited island.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sea holm \Sea" holm`\ (Bot.)
   Sea holly.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sea holm
    n 1: European evergreen eryngo with twisted spiny leaves
         naturalized on United States east coast; roots formerly
         used as an aphrodisiac [syn: sea holly, sea holm, sea
         eryngium, Eryngium maritimum]