Many variations on this sign. (Lots of different ways to kiss I reckon.)
Don't worry overmuch if someone doesn't kiss the way you do. Er...I mean,
doesn't do the sign "KISS" the way you do.
In the main version of this sign you form each hand into
flattened "O" handshapes and then you bring the fingertips together
in front of you while puckering up your lips (as if kissing
someone).
KISS:

Note: This version of KISS looks a lot like the sign for MORE.
Except MORE is done a bit lower and doesn't pucker up.
KISS (version)
This next version is also used by some people. The graphic is a bit
off. Instead the thumb is wrapped in a bit more and the tip or
pad of the thumb is pressed to the fingers. This version is
almost the same as the sign for HOME except that the KISS handshape
is much more flattened (but not totally flat -- it is more like an
extremely squished "O" hand.) Also for the sign HOME you don't
pucker up. But you do pucker up for all versions of KISS.

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American
Sign
Language (ASL) online at American Sign Language University ™
ASL resources by Lifeprint.com © Dr. William Vicars