The term GULLIBLE ONE is defined by six words: RUBE (4 letters), NAIF (4 letters), MARK (4 letters), DUPE (4 letters), PATSY (5 letters), and SAP (3 letters). RUBE is a slang term for someone who is naive or easily fooled. NAIF is a French word meaning naive or inexperienced. MARK is a slang term for someone who is easily taken advantage of. DUPE is a verb meaning to deceive or trick someone. PATSY is a slang term for someone who is easily fooled or manipulated. SAP is a slang term for someone who is easily taken advantage of. All of these words describe someone who is gullible or easily fooled.