Medical Definition of penicillin O
: a penicillin C13H18N2O4S2 that is similar to penicillin G in antibiotic activity but that is obtained by growing the penicillia in a culture medium that contains a precursor
a sum of money that is sent as a payment
Get Word of the Day daily email!
Love words? Need even more definitions?Merriam-Webster unabridged
Words at Play
Ask the Editors
- On Contractions of Multiple Words
- A Look at Uncommon Onomatopoeia
- Is Singular 'They' a Better Choice?
- Time Traveler Quiz: Which Word Came First? Take the quiz
- Slippery Words Quiz—Changing with the Times Take the quiz
- How Strong Is Your Vocabulary? Take the quiz
- Word Winder's CrossWinder Play the game