General synonyms:
* King of the beasts (figurative)
* Great cat
* Feline
* Predator
* Hunter
More specific terms:
* Lioness (female lion)
* Cub (young lion)
* Pride (group of lions)
* Mane (the distinctive hair growth around a male lion's neck)
* Roar (the characteristic sound a lion makes)
Other options:
* Leo (Latin name for lion)
* Panthera leo (scientific name)
* Royal beast
The best word to use will depend on what you are trying to convey.