slacken
verb (used with or without object)
to make or become less active, vigorous, intense, etc.
Used to describe an action that was ongoing continuously in the past up until another past event interrupted it.
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
During this conversation the horses had been slackening speed, and were only walking now.
From In Search of the Castaways; or the Children of Captain Grant by Jules Verne