Pécho is a French slang word for "seduce", mainly used in a sexual meaning (= "sleep with someone").
It is the verlan of choper which means attraper (to catch) and is used figurativlely to say "seduce".
Note that it is used as a verb and has only one form:

• Je pécho
• Tu pécho
• Il pécho

As for the plural form, "pécho" can only be used as a past participle: in the passé composé tense for instance:

• Nous avons pécho
• Elles ont pécho

etc.