Hesitation was a pause or delay in action, decision, or speech due to uncertainty, nervousness, or unwillingness.
In 2368, while speaking with Worf, Commander Kieran MacDuff said, "I am concerned about completing our mission, ending this war. In victory. We may soon face a critical moment. The success of our mission may hang on a split-second decision. A hesitation would kill us all, and those that are counting on us will surely die as well. We cannot let this happen. That'll be all." (TNG: "Conundrum")