What does it mean to be threadbare?

Frayed, worn, or shabby.

Alexa's eyes opened slowly and began to take in her surroundings in the dimness of the early morning light. Everything looked so familiar — the desk littered with stacks of magazines, the old rocking chair strewn with clothes, the threadbare rug, and the Avril Lavigne poster tacked to the wall, its edges badly frayed.

From Karen B. Chapman's The Mayan Mission.