A straitjacket is read as being held so tightly you cannot move or express yourself. Dream books link it to feeling restrained by rules, by expectations or by your own fears.
Where in your waking life have you met something like this lately?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.