Entry 1 sense Webster, 1913 Peninsula /pən-ĭn'-səl-ə/ · Pen·in·su·la · IPA /pəˈnɪn.sə.lə/ 01 n. A portion of land nearly surrounded by water, and connected with a larger body by a neck, or isthmus. 1. A portion of land nearly surrounded by water, and connected with a larger body by a neck, or isthmus.