Principal English Translation: 

one's equal, another like oneself (a necessarily possessed form; see Karttunen)

Orthographic Variants: 
Frances Karttunen: 

-POH a necessarily possessed form, one's equal, another like oneself / su igual, o su compañero (M), igualidad o semejanza (C) This is abundantly attested in C, R, and P. Modifying elements may intervene between the possessive prefix and the verb, NOPOH 'my equal, someone like me’, NOTLĀCAPOH 'a human being like myself,’ NOCNŌPOH 'someone poor like me.' This can be thought of as a preterit-as-present verb of the irregular type which takes possessive rather than subject prefixes and occurs only in singular form, in which case, it implies *POĀ 'to be, become like someone' S has absolutive potli, but it is nowhere attested in the sources for this dictionary.
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 200–201.

Attestations from sources in English: 

notlacapo = he is a man like me
yhuehuepo = he was as old as I (i.e., a parter, companion, or equal in age)
Rebecca Horn's notes from Nahuatl classes with James Lockhart, now in the possession of Stephanie Wood.