a flat canopy (especially one over a four-poster bed)
"The heavy velvet tester draped elegantly over the antique four-poster bed added a touch of royal luxury to the bedroom."
A canopy over a bed.
"The antique dealer identified the tarnished tester as a rare specimen from 15th-century France."
A person who administers a test.
An old French silver coin.
In plain English: A tester is someone who checks out new products to see if they work well before everyone else buys them.
"Before buying shoes, I tried them on in the store tester to check if they fit properly."
A surname.
"The Tester family has lived in the valley for generations."
The word tester comes from the Old French term testre, which was borrowed into Middle English from the Latin testura. Originally referring to a woven fabric or netting used for testing materials, it eventually came to mean an instrument designed for examination or evaluation.