The answer to the crossword for the term ONE IN 100 ABBR. is SEN, which stands for 'SENATOR'. A SENATOR is a member of a senate, which is a deliberative assembly, often the upper house or chamber of a bicameral legislature. Senators are typically elected by popular vote and serve for a fixed period of time. IN the United States, each state elects two senators, while IN other countries, the number of senators may vary.