To fasten or tighten something with a screw or screws. He screwed the shelf to the wall to ensure it was secure.
To twist or turn something in a spiral motion. She screwed the cap back onto the bottle tightly.
To cheat or deceive someone. He felt like he was screwed over by the contractor who didn't finish the job.
To have sexual intercourse with someone (informal and often considered vulgar). They were caught screwing in the backseat of the car.
To mess up or make a mistake. I really screwed up the presentation by forgetting my notes.