Using flash cards, drawing pictures and writing contextual sentences are good ways to learn math vocabulary. Learning math specific vocabulary is very similar to learning any other kind of vocabulary.
When making flash cards, put the math term on one side and the definition of the term on the other side. Make yourself familiar with the terms by reading each term and definition out loud. Then begin to test yourself by looking at the term and reciting the definition from memory, or the other way around. Set cards that you get correct immediately in one pile, and place cards that you have trouble with in another pile. This makes it easy to know which terms you need to study more thoroughly.
Drawing pictures is another good way to cement definitions of terms in your brain. These drawings can be added to your flash cards or kept separately in your notes or on a word wall. Some terms, like "parallel" are easy to draw pictures for, while others, like "multiply" might be more difficult to come up with a picture for. Try to come up with pictures for both the easy and the hard terms, however, because the next time you try to remember the word, you will remember coming up with the picture. This may also help you remember the definition.
Contextual sentences can also help you to remember definitions. This method simply involves writing a sentence containing the math term in a way that makes sense. For example, for the term "slope," you could write the sentence: "My sled went down the hill very fast because of the hill's large slope." This would help you remember that slope has to do with how steep a line is.