a bad or unsuitable match
"The bright orange tie looked like a terrible mismatch against his navy blue suit."
Something that does not match; something dissimilar, inappropriate or unsuitable.
"The bright yellow umbrella looked like a stark mismatch against the dark gray sky."
match badly; match two objects or people that do not go together
"The bright yellow umbrella looked like a terrible mismatch against the gloomy gray sky."
To match unsuitably; to fail to match
"The bright red umbrella was a total mismatch against the dull gray sky, making it look out of place in the crowd."