Definition, yes. But an etymology is more useful than just a definition. At least, I find them more useful, and I'm more likely to remember a word if I know where it comes from.
etymonline has some helpful info - it comes from latin res meaning "thing." So, basically, thing-ification.
reification (n.)
1846, "mental act of materializing (a person or concept), objectivization, the regarding or treating of an idea as a thing," from Latin re-, stem of res "thing" (see re), + -fication "a making or causing." In Marxist writing, "depersonalization," translating German Verdinglichung. https://www.etymonline.com/word/reification