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Related to flatten out: call on, in favor
flatten someone or something out
to make someone or something flat. If you fall under the steamroller, it will flatten you out. Flatten out that dough a little more. Please flatten it out.
1. To become completely flat: The graph indicated that sales were strong in July but that they flattened out in August.
2. To make something completely flat: I flattened out the crumpled paper and wrote on it. The iron flattened the wrinkly fabric out.
3. To knock someone to the ground: The boxer flattened out his opponent. The bicyclist flattened the pedestrian out.