1.
Something that happens ~ happens three times. (OLD-FASHIONED)
They should think not twice, but ~, before ignoring such advice...
She plays tennis ~ weekly.
ADV: ADV with v, ADV adv, ADV n
2.
You can use ~ to indicate that something is three times the size, value, or intensity of something else. (OLD-FASHIONED)
...moving at ~ the speed of sound.
ADV: ADV n