* Palindrome: A word that reads the same backward as forward (e.g., "racecar", "level"). While not technically opposites, they exhibit a form of self-reversal.
* Words with dual meanings: Some words have opposite meanings depending on context (e.g., "cleave" can mean to cut apart or to stick together).
* Words with antonyms that are close in meaning: Some words have antonyms that are almost synonymous (e.g., "hot" and "cold" could be considered opposites, but they both refer to temperature).
* Words that refer to their own negation: This gets a bit philosophical, but consider "nothingness" or "non-existence." They are concepts that essentially define the absence of themselves.
Let me know if you had a specific kind of word in mind, and I might be able to give you a more precise answer!