noun
plural buckles
[count] :a metal or plastic device that is attached to one end of a belt or strap and that is used to connect it to the other end
verb
buckles; buckled; buckling
[+ obj] to fasten (something, such as a belt) with a buckle
to attach (something) with a buckle
[no obj] :to bend or collapse from pressure, heat, etc.
[+ obj] :to cause (something) to bend or collapse
buckle down
[phrasal verb] informal :to start to work hard
buckle up
[phrasal verb] US :to fasten your seat belt in a car or other vehicle