When you streamline something, you're simplifying it to make it more efficient or profitable.
When you think of streamlining, think of a bunch of streams coming together to form one stream. This word is about taking something complicated with a lot of parts and turning it into a simpler, sleeker thing. When companies streamline, they cut staff and reorganize to make the business run more smoothly and make more money. When an engineer streamlines a car design, he takes out all the unnecessary parts and makes the engine more efficient.