WORCESTER, Mass. - Is a burrito a sandwich?

The Panera Bread Co. bakery-and-cafe chain says yes. But a judge said no, ruling against Panera in its bid to prevent a Mexican restaurant from moving into the same shopping mall.

Panera has a clause in its lease that prevents the White City Shopping Center in Shrewsbury from renting to another sandwich shop. Panera tried to invoke that clause to stop the opening of an Qdoba Mexican Grill.

But Superior Court Judge Jeffrey Locke cited Webster's Dictionary as well as testimony from a chef and a former high-ranking federal agriculture official in ruling that Qdoba's burritos and other offerings are not sandwiches.

The difference, the judge ruled, comes down to two slices of bread versus one tortilla.

"A sandwich is not commonly understood to include burritos, tacos and quesadillas, which are typically made with a single tortilla and stuffed with a choice filling of meat, rice, and beans," Locke wrote in a decision released last week.

In court papers, Panera, a St. Louis-based chain of more than 900 cafes, argued for a broad definition of a sandwich, saying that a flour tortilla is bread and that a food product with bread and a filling is a sandwich.

Qdoba, owned by San Diego-based Jack in the Box Inc., called food experts to testify on its behalf.

Among them was Cambridge chef Chris Schlesinger, who said in an affidavit: "I know of no chef or culinary historian who would call a burrito a sandwich. Indeed, the notion would be absurd to any credible chef or culinary historian."