A more thorough explanation:

Definition: One who humbly requests something; specifically, the actor in a petition of right.

Example: The suppliant begged the king for mercy.

Explanation: In this example, the suppliant is someone who is asking the king for mercy in a humble and respectful way. The suppliant is not demanding anything, but rather is making a request in a polite manner. This is the essence of being a suppliant - asking for something in a humble and respectful way.