Entry 1 sense Webster, 1913 Water hyacinth /wôt'-ẽr hī'-əs-ĭnthˌ/ · Wa·ter hy·a·cinth · IPA 01 Either of several tropical aquatic plants of the genus Eichhornia, related to the pickerel weed. 1. Either of several tropical aquatic plants of the genus Eichhornia, related to the pickerel weed.(Bot.)