(verb)
to hold someone firmly or be otherwise closely engaged, for example a grapple in a boxing match or an embrace;
e.g. The boxer tried to clinch his opponent before landing a blow.
(verb)
to fasten something by driving a nail through and then flattening or turning the protruding pointed end;
e.g. Once I clinch this nail, the two pieces of wood will be secured together.
(noun)
a physical fight or scuffle/struggle in which the fighters are very closely engaged, especially in boxing;
e.g. He attempted to escape from the clinch so he could attack his opponent.
(noun)
an instance of holding someone close in an embrace;
e.g. I saw them in a clinch, so they have resolved their argument.
(noun)
a type of knot used to attach a length of rope to a ring or a loop of rope, in which the end of the rope is seized back on itself;
e.g. She tied a clinch in the rope and then threw it on the ground.