Let a slip pass

• Assented, at an auction
• Dozed, with "off"
• Agreed silently
• Silently agreed
• Silently assented
• By playing three of diamonds one indicated support
• Signed an agreement?
• O.K.'d silently

WordNet Word definitions in WordNet
n. a sign of assent or salutation or command the act of nodding the head [also: nodding , nodded ]