The noun "brede" is an interwoven pattern—it comes from the same root as "braid." Although Keats is using it literally to describe the art presented on the urn, notice how it also characterizes the rich weave of thoughts, images, and philosophical questions the poem itself presents.
"All breathing human passion far above..."See in text(Ode on a Grecian Urn)
The "happy love" portrayed on the urn proves itself to be far better than human love or "passion," which necessarily decays with time and becomes less beautiful and less pure as it goes. "Breathing" here is synonymous with "mortal" and "temporary."
"What maidens
loth..."See in text(Ode on a Grecian Urn)
The adjective "loth" means "reluctant" or "unwilling," as in "bashful maidens." From this description, we can assume that there is a scene depicted on the urn wherein several men or gods address a group of women, likely in a romantic overture. These women, though beautiful, shy away from their advances.
"Cold Pastoral..."See in text(Ode on a Grecian Urn)
Broadly speaking, the "pastoral" refers to the ideal state of nature. Its roots are Latin, pastoralis meaning the tending of livestock. In poetry, the pastoral is a type of poetry that glorifies the natural world. The urn is characterized as a "Cold Pastoral" because its scenes move from the ideal to the realistic, incorporating images of sacrifice and suffering.
The verb "tease" here operates in both the amorous sense (a nod to the "marble men and maidens" teasing one another) and the literal sense—that is, to provoke or disturb. The the urn, with its antique, layered images of timeless human stories, stuns the speaker into a confrontation with eternity.
Here, "overwrought" can refer either to the urn's interwoven (overly elaborate) decoration or to the maidens' state of heightened emotion, which now appears to the speaker as being melodramatic or "cloy'd," as the aforementioned "human passion."
