A "button tab" is a small strip of fabric or material that has a button on one end and a hole or slit on the other. It is used to fasten or secure something, like folding over a cuff or holding a garment in place. Full definition
The vest fit great and had button tab sides, which give the vest a little more shape, so you can be warm and not boxy. (pumpsandpushups.com)
The silicone sleeve on this container helps prevent it from breaking, while button tabs ensure a leak - free fit. (health.com)
The shoulder straps have little button tabs underneath to keep your bra straps secured and concealed — it's always a treat to discover this nifty feature! (extrapetite.com)