The term 'MOST SURLY' can be defined by two crossword solutions: MEANEST (7 letters) and CRUSTIEST (9 letters). Both words describe someone who is unfriendly, uncooperative, and difficult to deal with. MEANEST implies a person who is intentionally cruel or unkind, while CRUSTIEST implies a person who is irritable and hard to please. Both terms are often used to describe someone who is unpleasant and unapproachable.