moulder

UK: /ˈməʊldə^r/

Collins Concise English Dictionary © HarperCollins Publishers::

moulder, molder / ˈməʊldə/ verb

1. (often followed by away) to crumble or cause to crumble, as through decay

Etymology: 16th Century: verbal use of mould³

WordReference Random House Learner's Dictionary of American English © 2025

mold•er¹ /ˈmoʊldɚ/   v. [no object]

1. to turn to dust by natural decay:
   The books were left moldering in the library for decades before anyone discovered them.

WordReference Random House Unabridged Dictionary of American English © 2025

mold•er¹  (mōl′dər), v.i. 

1. to turn to dust by natural decay;
   crumble;
   disintegrate;
   waste away:
   a house that had been left to molder.

v.t. 

2. to cause to molder.

• obsolete mold to crumble (verb, verbal use of mold³) + -er⁶ 1525–35

mold•er²  (mōl′dər), n. 

1. a person or thing that molds.
2. a person who makes molds.
3. Printing one of a set of electrotyped plates used only for making duplicate electrotypes.

• 1400–50; late Middle English; see mold¹, -er¹

Collins Concise English Dictionary © HarperCollins Publishers::

molder / ˈməʊldə/ verb , noun

1. the US spelling of moulder1