1. Bear down on: to move quickly towards someone in a determined and threatening way Example: "I could see a police car bearing down on us." 2. to push or press downwards Examples: It’s a natural instinct for a woman giving birth to bear down. The structure is positioned to bear down on its supports. This is from McMillan dictionary

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bear down v. 1. exert a force with a heavy weight 2. to make a rush at or sudden attack upon, as in battle 3. contract the abdominal muscles during childbirth to ease delivery 4. exert full strength 5. pay special attention to 6. exert a force or cause a strain upon