Colloquially, this
symbol is referred to as
the conductor's eye: the dot being the
eye, and the curve being the eyebrow.
When working with the youngest students, this is one of my favourite definitions: I tell the student that in a orchestra, when you have a note held for a duration longer than indicated by the note itself, the conductor will grill you with his eye for as long as he wants you to hold the note. (In an orchestra, these decisions are made by the conductor.)
And then, I pull my glasses down to the edge of my nose, and stare over them at my student.