吐痰是指将口中涶沫或其他分泌物吐出的行为。不同的年代和地区对吐痰有不同的理解。

于欧美很多地方，向别人的脸上吐痰代表对对方的极度鄙视、憎恨、不满。

在很多已发展地区，随地吐痰被视为极不文明的行为，而在中国和美国，此举却相当常见。

Spitting is the act of forcibly ejecting saliva or other substances from the mouth.

It is currently considered rude and a social taboo in many parts of the world including the West, while in some other parts of the world it is considered more socially acceptable. It is commonly believed that it is possible to transmit infectious diseases in this way, including tuberculosis, influenza, and the common cold but the epidemiological evidence that this is the case is not present and it is likely that this belief, although intuitive, is not reflective of meaningful risk.