What degree is crosswind?
Manu H has given what, to me, sounds like as close to a textbook answer as you can get.
Crosswind is always 90° to your direction of travel. You base crosswind off of your track instead of your heading. Regardless of your track or heading, or the wind direction, the crosswind intensity would be a percentage of the total wind intensity ranging from 0% to 100% coming from 90° to your direction of travel. You can find the numeric value of the crosswind using Pythagorean’s Theorem. The headwind/tailwind component and the crosswind  component make up two of the legs of the mathematical 90° triangle. The actual wind bearing from your direction of travel and its intensity make up the hypotenuse.
Or, you can use the graph, below: