Texas A&M University sued the Indianapolis Colts on Thursday, saying the NFL team has violated its trademark "The 12th Man" through the unauthorized use of the phrase in marketing material and merchandise.

The university has been aggressive in defending the trademark associated with its nearly century-old tradition of "The 12th Man," taking on the likes of the Seattle Seahawks football team and a double amputee in Buffalo it suspected of trademark infringement.

In the lawsuit, filed in U.S District Court in Houston, Texas A&M said its marketing connections to "The 12th Man" is likely being tarnished by the Colt's unauthorized use.

"We're aware of the media reports of the Texas A&M lawsuit but we've not yet had an opportunity to review the actual complaint," a Colts spokesman said.

According to the lawsuit, "The 12th MAN Mark was initially adopted in 1922 as a remembrance of a student at Texas A&M, E. King Gill, and his spirit of readiness to serve Texas A&M’s football team in time of need."

A dispute over the use of the phrase to refer to the fans of the Seattle Seahawks was settled in 2006, with the Seahawks paying a licensing fee and acknowledging the phrase it is the trademarked property of the Texas university.

Texas A&M President Michael Young says the university contacted the Colts at the same time and informed them it trademarked the phrase in 1990. He says the Colts did not adequately address the university's claims.

"We would prefer not to file lawsuits to protect our trademarks," Young said in a statement.

"However, when our intellectual property, especially the 12th Man Mark, which is so important to our students and former students, is used without our permission after repeated attempts to engage on the matter, we are left with no choice."

In 2006, the university sent a cease and desist letter to the Colts and was assured by the team that it wanted an amicable outcome, and the Colts would not use the 12th Man beyond its stadium.

Over the next several years, Texas A&M became aware of new uses of the 12th Man, and in July 2105, it said the Colts used a "Join the 12th Man" in solicitations for football tickets. The team also used the phrase in Colts-branded items sold over the NFL's Internet shop, the lawsuit said.

There was no monetary amount for damages mentioned in the lawsuit.