An online thesaurus struck a listing Monday for the word "Arab" after Arab-American groups complained the entry listed derogatory synonyms. The entry, which appeared on thesaurus.com, listed the word as a noun meaning "beggar," and gave 16 pejorative synonyms including "homeless person" and "welfare bum." The American Arab Anti-Discrimination Committee contacted the synonym book's online publisher Friday to complain about the entry; the American Arab Forum also criticized the listing on Monday. "I looked it up and I couldn't believe what I was seeing," said Aref Assaf, president of the American Arab Forum, which is based in Paterson.