plumbs
Plumbs is not the standard plural for the fruit commonly called plum; the usual plural is plums. The term also occurs as a form of the verb to plumb and, in some technical contexts, as a plural for a plumb line or plumb bob used in measurement.
Plumb as a noun refers to a lead weight attached to a line used to determine verticality.
As a verb, to plumb means to measure depth or to determine vertical alignment. The third-person singular
Fruit context: the edible fruit of the genus Prunus is called plum; the plural is plums. Plums