A useful tool for your Clil lessons

Math Dictionary for Kids is an excellent helper for kids.

This interactive dictionary allows users to search for terms, mark favourites for studying further, take notes on definitions and see related terms. It includes illustrated and clear explanations of the most common terms used in math lessons, categorized by alphabetical scroll list. 
I highly recommend it!

Free on-line English dictionary

Kids Wordsmyth is a great visual dictionary that I learned about through Richard Byrne blog. 
It is a type of resource that I like to link to and feature prominently on this blog (useful webs for children, right side).

Students can search for words, hear them pronounced, read definitions and see illustrations of words as I said. Thus, when they don't understant the definition, the picture could help students grasp the description of the word.

Also, the dictionary is arranged in a virtual book with tabs for each letter of the alphabet.