- One who or that which expands; especially, a tool or machine used to expand something; specifically, in <em>plumbing</em>, a tool used to spread lead-packing into the inner flange-recesses of pipe-connections.
- A tool used to secure a tube in a plate or sheet so that the joint shall be steam- or water-tight under pressure.
- Anything which causes expansion esp. (Mech.) a tool for stretching open or expanding a tube, etc.
- <xref>Agent noun</xref> of <xref>expand</xref>; someone or something that expands.