Definition of R factor
: a group of genes present in some bacteria that provide a basis for resistance to antibiotics and can be transferred from cell to cell by conjugation
Love words? Need even more definitions?Merriam-Webster unabridged
Words at Play
Ask the Editors
Name That Thing MegaQuiz: Vol. 2
Test your visual vocabulary!
Favorite New Words in the Dictionary
Level up your vocabulary with these newly added w...
How Strong Is Your Vocabulary?
Test your vocabulary with our 10-question quiz!
Spelling Bee Quiz
Can you outdo past winners of the National Spelli...