Mum-and-dad investor

What is Mum-and-dad investor?

Mum-and-dad investor definition and meaning on Dictionary terms:
verb (used without object), mumA.bled, mumA.bling.
to speak in a low indistinct manner, almost to an unintelligible extent; mutter.
to chew ineffectively, as from loss of teeth: to mumble on a crust.

verb (used with object), mumA.bled, mumA.bling.
to say or utter indistinctly, as with partly closed lips: He mumbled something about expenses.
to chew, or try to eat, with difficulty, as from loss of teeth.

a low, indistinct utterance or sound.