Dilation

[Jason Yan]

The act of dilating, or the state of being dilated;
expansion; dilatation.

[Little_Girl]

The expanding of the vagina or anus by means of inserting [plugs] that are [gradually] larger, or by inserting [a plug] that can be expanded by a ratchet or a pump.

[Mark Zuckerberg]

The action or condition of becoming or being made wider, larger, or more open.

[Gregory]

the state of being larger or more open than usual