Overfullness; especially, excessive fullness of the blood vessels; repletion; that state of the blood vessels or of the system when the blood exceeds a healthy standard in quantity; hyperæmia; opposed to anæmia
A plethora of something is a large amount of it, especially an amount of it that is greater than you need, want, or can cope with. A plethora of new operators will be allowed to enter the market. a plethora of sth a very large number of something, usually more than you need (, from plethein )