S: (adj) inert, indifferent, neutral (having only a limited ability to react chemically; chemically inactive) "inert matter"; "an indifferent chemical in a reaction"
S: (adj) neutral (not supporting or favoring either side in a war, dispute, or contest)
S: (adj) neutral (possessing no distinctive quality or characteristics)
S: (adj) achromatic, neutral (having no hue) "neutral colors like black or white"
S: (adj) neutral (lacking distinguishing quality or characteristics) "a neutral personality that made no impression whatever"