In a way that shows great knowledge, insight, or understanding. It can also mean to an extreme or intense degree.
From Latin 'profundus' meaning 'deep', composed of 'pro-' (forward) and 'fundus' (bottom). The sense evolved from physical depth to intellectual or emotional depth by the 14th century.
The word carries both intellectual and spatial metaphors - when we understand something profoundly, we're metaphorically diving to the 'bottom' of it. Interestingly, the ocean's 'profound zone' uses the same root, referring to the deepest waters where sunlight never penetrates.
Complete word intelligence in one call. Free tier — 50 lookups/day.