A Wonderfully Illustrated Definition

pre·cur·sor 
n. 1. One that precedes and indicates, suggests, or announces someone or something to come: Colonial opposition to unfair taxation by the British was a precursor of the Revolution.
2. One that precedes another; a forerunner or predecessor: The new principal's precursor was an eminent educator.
3. A biochemical substance, such as an intermediate compound in a chain of enzymatic reactions, from which a more stable or definitive product is formed: a precursor of insulin.
[Middle English precursoure, from Old French precurseur, from Latin praecursor, from praecursus, past participle of praecurrere, to run before : prae-, pre- + currere, to run; see kers- in Indo-European roots.]
Via thefreedictionary.com

Thanks for the laugh, Wrong Hands.