A hat tip is an act of tipping or (especially in British English) doffing one's hat as a cultural expression of recognition, respect, gratitude, greeting, or simple salutation and acknowledgement between two persons. In Western societies of the 19th and early 20th centuries, a hat tip was a common non-verbal greeting between friends or acquaintances while walking on a sidewalk or meeting at a social gathering. Typically, two men (female hat tipping was rare) would lift or tip their hats to each other, rather than exchange words of greeting. Where the ritual was used to emphasize social d...