Definition:
Gassho is Japanese for "palms of the hands placed together." The gesture is made as a greeting, in gratitude, or to make a request.
In the most common form of gassho used in Japanese Zen, hands are pressed together, palm to palm in front of one's face. Fingers are straight. There should be about a fist's distance between one's nose and one's hands. Fingertips should be the same distance from the floor as one's nose. Elbows are held slightly away from the body.
Gassho often accompanies a bow. To bow, bend only at the waist, keeping the back straight.
