Mix together the ingredients or parts, as in He stirred up some pancake batter, or Will you stir up the fire? [Mid-1300s]
Rouse to action, incite, provoke, as in He's always stirring up trouble among the campers, or If the strikers aren't careful they'll stir up a riot. [First half of 1500s] Also see stir up a hornets' nest.
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