fer·til·iz·er \-zə(r)\noun (-s) 1.: one that fertilizes < he was not only a very distinguished writer but … a fertilizer of other talents — Lloyd Morris > 2.: a substance (as manure, lime, or commercial fertilizer) used to fertilize soil; especially: one chemically prepared that supplies nutrients (as a mixture containing varying percentages of nitrogen, available phosphate, and water-soluble potash)