Noun
left bower (plural left bowers)
(euchre) The jack of the other suit of the same colour as the trump (whose jack is called the right bower), and next to it in value.
In Euchre, the highest trump card is the Jack of the trump suit, called the right bower (from the German Bauer); the second-highest trump, the left bower, is the Jack of the suit of the same color as trumps. Source: Internet
Players must follow suit if they can (This includes the left bower or any other card that is considered a trump, if trumps are led). Source: Internet