Sometimes, he thought it was worth it to have her smiling when she opened the front door in the cold twilights, kissing him on the ear or the nose or some other inappropriate place, to feel her head snuggling drowsily on his shoulder at night under warm quilts.
There are no more uses of "appropriate" identified with this meaning, but check unspecified meaning below.
Don’t you think, even if it was a lie, that it would be appropriate for you to say ’I love you, Rhett,’ even if you didn’t mean it?
She remembered him coming home from Charleston and Atlanta laden with gifts that were never appropriate, remembered too, with a faint smile through tears, how he came home in the wee hours from Court Day at Jonesboro, drunk as seven earls, jumping fences, his rollicking voice raised in "The Wearin’ o’ the Green."
There are no more uses of "appropriate" in the book.