To resist something means to fight against it or try not to let it happen. It's like trying to hold back a strong force.
When we talk about resisting something, we usually mean that we don't want it to affect us or change our lives in some way. For example, when you're feeling tired but still have a lot of work to do, you might resist the temptation to take a nap and instead keep working. You're fighting against your tiredness and trying to stay focused. Or maybe someone is trying to convince you to try something new that makes you uncomfortable - in that case, you might resist their suggestion because it's not what you want to do.
A protective coating or covering.
To attempt to counter the actions or effects of.
