How do I explain to an ESL the term "To be nervous"?

Do they speak Mandarin or Cantonese? You're taking too much time -- it's only an idiom. Google: translate nervous into Cantonese (or Mandarin) They'll give you something that you probably won't pronounce right, but someone will get it. If you get characters, print it out and show it to someone. Also, mime it. You can use "afraid" for a synonym.