A person (usually female) with no visible means of support who manages to live well off of gifts from the opposite sex as well as availing themselves of any source of free product (ie. party snacks, restaurant condiment packages, hotel soap). Different than a prostitute/gigolo/mistress because they are not selling sex acts and usually do not have one long-term resource (ie. 'sugardaddy').
"See that girl by the bar? She's a scrabbler, she hasn't paid for a drink of her own all night"
"Lots of girls on these dating sites are scrabblers, they just want guys to pay for their food and entertainment with no real intent of getting involved"