Tacit assent is a form of agreement that is implied rather than expressed directly. It is often used in situations where one party agrees to something without actually saying so. The term 'tacit assent' is derived from the Latin word tacitus, which means silent or unspoken. The crossword solution for the term 'tacit assent' is 'NOD, ' which implies a gesture of agreement. Nodding one's head is a common way of expressing agreement without actually saying anything.