Syllable division and stress derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
pecos is a noun meaning "a tributary of the Rio Grande that flows southeastward from New Mexico through western Texas". It carries one recorded sense.
a tributary of the Rio Grande that flows southeastward from New Mexico through western Texas
Forms marked are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for pecos come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.