The antonyms for the word "shake out" are limited but opposite in meaning. Instead of shaking out, you can gather or collect things in one place. The term "shake in" means the opposite of shaking out. This means to add something new or include something. The term "settle in" is also an antonym for shake out. This term means to make something stable or secure, instead of shaking it out. Additionally, "pack up" can be an antonym to shake out because packing things up is the opposite of shaking them out. In short, the opposite of shake out is to gather, add, settle, and pack up things.