To snubstitute is to non-consensually replace something that belongs to another person with something of lesser value.
Likewise, a snubstitute teacher is a substitute teacher that is actually more annoying than your regular teacher.
1) "Jimmy snubstituted my Coke for Diet Coke again, what the hell?"
2) "Mrs. K is horrible I hate her. She's more like a snubstitute teacher."
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