if a court case is undefended, no one argues against it. In some jurisdictions, an undefended case is one where the defendant does not reply or react to any correspondence from the court saying that there is a case against them and does not appear in court to defend the case.
The charges were undefended.
(of a defendant in a lawsuit) with no legal representation ie no lawyer speaking on your behalf
Ruiz and Ortega are represented by Bryan Neal, while the others are undefended.
(of a building, town, city, or country etc) with no guards, soldiers, or military etc to defend against attack
Reports say the town was left undefended because of the belated deployment of troops stationed there to search for the missing schoolgirls.