The Virginia Supreme Court appeared sharply critical today of a lower court ruling blocking an unmarried woman from taking the state bar examination because she lives with a man.

Although the court did not rule on the woman's appeal today, the seven justices showered critical questions on a state lawyer defending Circuit Court Judge Duncan C. Gibb, who blocked Bonnie C. Cord from practicing law in the state. Cord, 34, a graduate of Georgetown University Law School, works as a lawyer for the Energy Department in Washington and lives in Warren County, about 45 miles west of the capital.

Her lawyer told the court today that Cord was a victim of sex discrimination. Virginia has never sought to block a man from taking the bar examination for deviating from moral standards, said Thomas V. Monahan of Winchester, Cord's lawyer. "There does appear to be an invidious approach taken in this case," he said.

Most of the court's attention today, focused on questions of whether Gibb applied one standard of conduct for prospective lawyers and another for members of the bar and whether he had based his ruling solely on his personal views.

When he ruled against Cord, Gibb overruled a 2-to-1 recommendation by a committee of lawyers, saying that he found her living arrangment "might lower the public's opinion of the bar us a whole." Although Cord is a member of the bar of the District of Columbia, she is not permitted to practice law in Virginia without taking the bar examination or receiving specific approval to practice there.

Justice Richard H. Poff today asked Assistant Attorney General Valentine W. Southall Jr. if Gibb's ruling would require disbarment of unmarried lawyers who live with members of the opposite sex.

Southall answered that it would. He added, however, that anyone charging a practicing lawyer with bad moral character would have the burden of proving the allegation while an applicant for the bar bears the burden of proving good character.

"What we have here is an admission near to a criminal violation," Southall said. "She didn't meet her burden of proof."

Although Southall contended that Cord's affidavit describing her living arrangement suggested a criminal violation, he said he would not recommend a charge on that evidence if he were a prosecutor.

In an affidavit, Cord said she intends to marry the man with whom she lives.She said the premarital arrangement is an effort to avoid problems that arose in her first marriage, which ended in divorce.

Cord's lawyer contended that the court should rely on testimony by character witnesses for Cord. They said her living arrangement was known to them "but not a matter of discussion in the community."