Vocabulary

I am grading my students' projects that they completed after reading their independent reading books (of their own choice). One of their options was a vocabulary project: "Keep a list of words you don't know while you're reading your book. When you finish, pick 15 of these words. You must define them and use each in a sentence with context cues. Then create some kind of vocabulary activity that would help fellow students learn your words (a crossword puzzle, word find, fill in the blank using your sentences, etc.). Include an answer key."

I don't know how to grade these fairly, especially when the student's first language is not English, so that their only exposure to these words is probably through books.

GRIM: Harsh, forbidding.
"I'm so harsh with my brother, im grim all the time"

SACRILEGE: An act of disrespect or violence.
"Stop acting sacrilege to your brothe, so violent"

RIBALD: vulgar lewd humor.
"Your so funny, so ribald."

LITHE: easily bent or flexed.
"Metal can be very lithe while heated."

MANGY: affected with or resulting from mange. Example, chicken pox the holes from chicken pox.
"I have mangy skin due to the sun's rays."

I do know that I obviously need to point out that if they don't know the words in the definition for their vocabulary word, they have to look those up, or they aren't going to know what the word means! Also that they need to be careful about the spelling and punctuation of all the words they use, not just the vocabulary words. But beyond that, I'm at a bit of a loss. Suggestions?

I do really like this one, in spite of the "from" which I think is just a typo:
USURP (no definition given)
"I usurp my neighbor's land, to get back at him from using my lawn for a garage sale."