dead set against
Completely opposed to, as in His parents were dead set against John's taking a year off from college. Set against has been used to mean “opposed to” since the 1400s. Dead acquired the meaning “utterly” in the 16th century.
Nearby words
dead run, dead sea, dead sea fruit, dead sea scrolls, dead set, dead set against, dead slow, dead soldier, dead space, dead spindle, dead spot
The American Heritage® Idioms Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.