weed
n. C / U C1 Advanced Oxford US //ˈwid// UK //wˈiːd// weed
n. a plant that grows where it is not wanted, like in a garden or a field. It is also a common informal name for the drug cannabis.
n. a wild plant growing where it is not wanted, typically in competition with cultivated species. Also used as a common informal synecdoche for cannabis.
I spent the whole afternoon pulling weeds out of the garden.
The abandoned lot was completely overgrown with tall weeds and rusted machinery.
Agricultural scientists are developing new methods to control invasive weeds that have become resistant to standard chemical treatments over several generations.
Usage
Countable when referring to individual plants in a garden; uncountable when used as a slang term for cannabis.