Principal English Translation: 

a narcotic, a hallucinogen (see Bierhorst, attestations)

Attestations from sources in English: 

"POYOMAHTLI, variant POYOMATL... apoc. var. POYON. A narcotic plant material (see HG bk. 10, ch. 24, para. 17; cf. FC 10:88, see also FC 10:56); a root that " reveals occult things and prophecies" (HERN 1: 105 ), narcotic flower of the CACAHUAXOCHITL (see FC 11:202 and 11:212)
John Bierhorst, A Nahuatl-English Dictionary and Concordance to the Cantares Mexicanos (1985), 273.