: to assume (something) as true, real, unquestionable, or to be expected
We took our invitation to the party for granted. = We took it for granted that we'd be invited to the party. [=we assumed we'd be invited and did not think about the possibility that we wouldn't be]
What I will call the "old" middle class rose to prominence in the Forties, Fifties, and Sixties, when economic growth was taken for granted and opportunity was abundant. Alan Wolfe
2
: to value (something or someone) too lightly : to fail to properly notice or appreciate (someone or something that should be valued)