A completely different word, or one with the last few letters changed?
For the first one, that's just a bad dictionary. Or someone trying to give you a very fast and rough definition.
Loathe: [0] "to dislike greatly and often with disgust or intolerance" Abhor: [1] "to regard with extreme repugnance : to feel hatred or loathing for : loathe"
Basically any word that means exactly the same as another word.
The SAT liked to do questions like Abhor is to Loathe like X is to Y.
[0] https://www.merriam-webster.com/dictionary/loathe [1] https://www.merriam-webster.com/dictionary/abhor