"Crash out" is an informal phrasal verb that means to fall asleep suddenly and heavily after feeling extremely tired. However, there are several other synonyms you can use instead of "crash out" in your daily conversations or writing. 1. Doze off: This phrase means to fall asleep, especially accidentally. 2. Nod off: This phrase means to fall asleep briefly, often while sitting up. 3. Drop off: This means to fall asleep quickly. 4. Snooze: This refers to a brief sleep, such as a nap. 5. Slumber: This means to sleep peacefully and deeply. Using these synonyms instead of "crash out" can add variety to your vocabulary and make your language more sophisticated.