the world > action or operation > behaviour > good behaviour > courtesy > courteous act or expression > [noun] > greeting or salutation > gesture > by slight movement of cap (2)
A half-courteous salute, shown by a slight movement only of the cap. Obs.
In figurative phrase a tip of the hat (or cap), an acknowledgement or mark of respect, in recognition of achievement, thanks, etc. See tip, v.2 2b…