Spitting
Spitting was the act of ejecting saliva or other substances from the mouth. Klingons frequently spat as an expression of contempt. 

In the holoprogram set during Earth's World War II, initiated by the Hirogen aboard , a holographic French citizen spit at Brigitte, a woman perceived to be collaborating with the Nazi occupiers. ()

In February 2152,  spat out a mouthful of water Jonathan Archer had boiled with a phase-pistol on stun. ()

Later that year, Tucker spat out a mouthful of "tarrat-aash" that Zho'Kaan had given him. ()

In 2153, while imprisoned on Narendra III, Archer spat out a piece of underdone targ. ()

In February 2154, Hoshi Sato spat in Dolim's face after he goaded her on her unwitting role in helping to destroy Earth. ()

In 2364 on Minos, Jean-Luc Picard spat out a piece of root he had sampled, declaring it to be very bitter. ()

In 2365, Danilo Odell spat into his hand before shaking hands with Wilson Granger. () 
 
In 2370, T'Kar spat on a Deep Space 9 airlock floor in contempt for the "doddering fools and frightened old women" whom he believed governed the Klingon Empire. ()

Later that year in the mirror universe, Telok spat in the face of a  Marauder who had collided with him. ()

In 2371, Grilka spat on her husband Quark as part of the Klingon divorce ceremony. ()

Later that year, Chakotay spat out some leola root moments after sampling it. ()

In 2373, Ortikan spat on the 's deck at the mention of Cardassians. ()

In 2374, Sirella spat on the ground after Jadzia Dax refused to perform the Bre'Nan ritual. ()
 
Soon after, Gul Dukat spat out a sample of his own cooking while preparing breakfast for himself and Benjamin Sisko. ()

See also 
 Spitting cobra
 Spitting termite

External link 
 
Physiology