(idiomatic) In spirit; according to one's beliefs, views or feelings; deep down, really, fundamentally.
I'm a vegetarian at heart - the thought of the death of animals for my food is abhorrent.
My dad may be old on the outside, but he's young at heart; he plays video games every now and then to improve his coordination.
At-heart Sentence Examples
Cathy is a large individual for a female and is young at heart.
Q. There are a number of very romantic moments in the film - are you a romantic at heart?
Others occur in the flat northern half of the Crimea, and even close to Kerch, where the famous Kul Oba seems to have held a Scythic chieftain who had adopted a veneer of Greek tastes, but remained a barbarian at heart.
His insight, however, did not extend beyond the circumstances immediately before and around him, and he failed to realize that the great mass of the French nation was still with Napoleon at heart.
Strange, too, as it may sound, Peter the Great was at heart profoundly religious.