(pathology) A potentially fatal condition in which one or more thrombi (or clots) form in the predominantly the leg or, more unusually, the arm. The clot may break free from the venous wall and travel via the circulatory system to the heart or to the lungs (causing a pulmonary embolism); this condition is often caused by keeping the legs bent for long periods but can also be caused by other medical problems.

Covering a large set of topics but on a very shallow level.

Alternative form of still waters run deep

A person with a calm appearance has, or may have, considerable inner emotion, character, or intellect.

What matters is a person's character, rather than his/her appearance.

Synonym of knee-deep in the Big Muddy

(chiefly US, idiomatic) Stuck in a predicament; mired in a difficult situation, especially one resulting from poor judgment or bad leadership.

(idiomatic) Between undesirable alternatives.