The term 'not feeling well' can be described in a variety of ways. The three letter word 'ILL' is often used to describe someone who is not feeling well, while the ten letter word 'INDISPOSED' is a more formal way of saying the same thing. The six letter word 'AILING' is another way of expressing that someone is not feeling well, as is the six letter word 'INFIRM'. Finally, the ten letter word 'outofsorts' is a colloquial way of saying that someone is not feeling well. All of these words are used to describe someone who is not feeling well, either physically or mentally.