There is no one definition for spitting. Also,
the way that your student spits may be more of a drool. What's important
is not the name of the behavior, but rather that it is described so well
and so precisely that others will know what you are looking for and would
record it's occurrence at the same rate as you.
Spits: Student propels saliva beyond his/her
lips. (Each attempt to propel saliva
is counted as one occurrence.)