Considerably, in the extreme; also, without restraint. For example, They were having money problems, in spades, or Jan told him what he really thought of him, in spades. This expression alludes to spades as the highest-ranking suit in various card games, such as bridge, and transfers "highest" to other extremes. [Colloquial; 1920s]

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Company. All rights reserved.