A more thorough explanation:

Definition: Capable of being legally admitted; allowable; permissible. Worthy of gaining entry or being admitted.

• Admissible evidence: Evidence that is allowed to be presented in court because it is relevant and obtained legally.
• Admissible to the bar: A person who has obtained a law degree and passed the bar exam is admissible to the bar and can practice law.

The examples illustrate that admissible refers to something that is legally allowed or worthy of being accepted. Admissible evidence is evidence that can be presented in court because it is relevant and obtained legally. A person who is admissible to the bar has met the necessary requirements to practice law and is considered worthy of being admitted to the legal profession.