Gabriel: Do you have any idea what this meeting is about today?
Katie: Apparently, we fell short of our monthly goal again.
Gabriel: Oh no! I thought sales were up this month.
Katie: Maybe in your department, but overall, our sales are down.
Meaning: The expression "to fall short (of)" means to fail to reach a target. It's often used with the preposition "of" when the target or goal is used as an object, as in the example above, where the company Gabriel and Katie work for failed to reach their monthly sales goal. It can also be used without "of," as in the next example:
Monica: Did you watch the game?
Wayne: What a disaster!
Monica: I know! I had such high expectations for our team, and they were winning in the first half!
Wayne: Yeah, they really fell short in the second half.
Meaning: Wayne uses the expression "to fall short (of)" to say that the team failed to reach their target of winning. Notice that because he doesn't mention what the goal was, he does not use "of."