tallest definition
: greater in height than the average person, building, etc. 1  All the children in my family grew up to be very tall. 2  My mother is short but my father is fairly tall. 3  The giraffe is the tallest animal. 4  tall trees. 5  the tallest [=highest] mountain. 6  the world's tallest building. 7  The drinks were served in tall glasses.