What is the meaning of the proverb "A nod's as good as a wink"?

The proverb 'a nod is as good as a wink' acknowledges that a hint or suggestion can be or has been understood without the need for further elaboration or explanation. An example in a sentence:

No need to tell me what you were up to last night - a nod's as good as a wink.

The proverb may sound modern but is in fact a 16th-century phrase originating in England. While it is the shorter version we hear more these days, the full version is 'a nod is as good as a wink to a blind horse'. The earliest examples of the proverb in print all give the fuller version, for example, in the Letters of the English lawyer and writer Joseph Ritson, February 1793:

A nod, you know, is as good as a wink to a blind horse.

More recently, the expression has gained momentum in the form of "a nod is as good as a wink to a blind bat", which was used in a Monty Python's Flying Circus sketch.