sem·i·o·chem·i·cal 
(sĕm′ē-ō-kĕmĭ-kəl, sĕm′ī-)
(sĕm′ē-ō-kĕmĭ-kəl, sĕm′ī-)n.
A chemical emitted by an organism that influences the physiology or behavior of an organism of the same or a different species, such as a pheromone or an allelochemical.
[Greek sēmeion, sign; see SEMIOTIC + CHEMICAL.]