The term 'suffix with neuro-' can be completed with the word 'plasm, ' which is a five-letter word. Plasm is a term used in biology to refer to a substance that makes up the living cells of an organism. It is composed of proteins, lipids, carbohydrates, and other molecules. The suffix 'neuro-' is used to refer to the nervous system, so the term 'suffix with neuro-plasm' refers to a substance related to the nervous system.