Water hyacinth \Wa"ter hy"a*cinth\ (Bot.) Either of several tropical aquatic plants of the genus {Eichhornia}, related to the pickerel weed.
water hyacinth n : a tropical floating aquatic plant having spikes of large blue flowers; troublesome in clogging waterways especially in southern United States [syn: {water orchid}, {Eichhornia crassipes}, {Eichhornia spesiosa}]