lower1. 1  to cause to descend; let or put down: to lower a flag. 2  to make lower in height or level: to lower the water in a canal. 3  to reduce in amount, price, degree, force, etc. 4  to make less loud: Please lower your voice.
Biggest Whale-Basilosaurus (60 Tons). Basilosaurus (Nobu Tamura). Unlike the other mammals on this list, Basilosaurus can't lay claim to being the largest-ever of its breed--that honor belongs to the still-extant Blue Whale, which can grow to as much as 200 tons.
The Blue Whale, the world's biggest whale. Wikimedia Commons. At about 100 feet long and 200 tons, not only is the Blue Whale the biggest mammal in the world today, but it's the largest vertebrate animal in the history of life on earth: not even the largest dinosaurs approached it in bulk.