The term SIGNAL AT SOTHEBY'S is composed of two crossword solutions, NOD and BID. NOD is a 3-letter word meaning to move one's head up and down in agreement or acknowledgement. BID is also a 3-letter word meaning to make an offer of a price for something. Sotheby's is an auction house founded in 1744 that specializes in fine art, antiques, and collectibles. Therefore, the phrase SIGNAL AT SOTHEBY'S could refer to a person nodding or bidding on an item at an auction.