If something is disproportionate, it is too much or too little when you put it next to something else. The size, the cost, the anger, the punishment — whatever it is — does not match. A small mistake with a huge punishment is disproportionate. A tiny worry that eats your whole week can be disproportionate too. The word is a little formal, but news writers and teachers use it a lot, often with to: “disproportionate to the risk”. People also stretch it: they call a reaction disproportionate when they feel someone has gone too far, even if they cannot measure the two sides. Though actually, in chat many people just say “too much” or “over the top”. There is a rare verb, to disproportionate, but the adjective is the form you will meet.