A Dilation

1. The act of dilating.
2. State of being dilated; expansion; dilatation. Synonyms: expansion, dilatation
3. (obsolete) Delay. Synonyms: cunctation, hold-up
4. (mathematics) In morphology, a basic operation (denoted ⊕) that usually uses a structuring element for probing and expanding the shapes contained in the input image.