A term used for Latinas who have a fairer complexion and lighter hair/eyes than their more darker Latina counterparts. It is not the same as a "gringa." It is important to note that in the spelling there is an umlaut above the letter "u" giving it a "w" sound, pronounced like "weda". Can be either derogatory or complimentary given the circumstances. The masculine form would be guero.
boy #1: Wow, she's Mexican? I would never have guessed she was with her green eyes and blonde hair.
boy #2: Ya, she's just a guera.