a strap on the upper of a shoe that extends backward from the vamp and joins with a strap that crosses the upper part of the instep, forming a T .
2.
a shoe having such a strap.
British Dictionary definitions for T-strap
T-strap
noun
1.
(modifier) denoting a type of woman's shoe fastened with a T-shaped strap having one part passing across the ankle and the other attached to it in the middle and lying along the length of the foot Also called T-bar