desnudar
undress
des-
un-, opposite of
+
nude
naked
+
-ar
verb suffix
Desnudar means to undress and can be thought of as des-0 (un-, opposite of0) + nude1 + -ar2 (verb suffix2), literally meaning 'to un-nude' or remove clothes.
verb
  1. undress
    To remove clothing from someone or oneself.
    El médico le pidió que se desnudara para el examen. // The doctor asked him to undress for the examination.