A more thorough explanation:

ADVERSUS

Adversus (ad-vər-səs) is a Latin preposition that means "against." In legal reports, the first letter of this term was previously used instead of the more commonly used "v." (versus). It is abbreviated as "a."

• The defendant argued adversus the plaintiff's claims.
• The case of Smith adversus Jones was heard in court.

These examples illustrate the use of adversus to indicate opposition or conflict between two parties in a legal context.