As Dane Archer says, "The potential for confusion, embarrassment, or conflict is clear." He suggests that individuals going to travel or work in another society need to be sensitive to unfamiliar gestures, and conscious that their own gestures may not be recognized, or misinterpreted, in the other culture.
Archer tells the story of a man who was on a boat touring the Nile. A group of Egyptians along the shore were gesturing with their arms. The man gestured back, thinking it was some kind of a greeting. Unfortunately for the tourist, they had been giving him some kind of very insulting message, and there was nearly a riot when he came to shore.
Archer says that one of the most striking thing about the multitude of gestures is their subtlety. "Differences that are slight or small in scale can have enormous consequences," says Archer.
In Germany and other European cultures, the sign for stupid is a finger held to the forehead, while in the United States, the sign for smart is a finger held only inches away, at the temples. "Even though these positional or motion differences seem slight, the change in meaning can be enormous."
For example, "OK" in the United States means "money" in Japan, "sex" in Mexico, "obscenity" in Brazil, and "homosexual" in Ethiopia. These may all be OK for the gesturing person, but then again, they may want to know what they are signaling to a native of Mexico or Ethiopia.
"Good luck" (thumbs up) in the U.S. means "sit on this" in Sardinia and "screw you" in Iran.
The "V" for victory that Winston Churchill used was reversed by Margaret Thatcher during a speech when she flashed an obscene gesture to a crowd (see United Kingdom). George Bush did the same thing in Australia. This could come as a shock to a mellow traveler who gives someone the peace sign in a Commonwealth country and is actually telling them to fuck off. Peace, man.