Definition of Rift Valley fever
: an acute, usually epizootic, mosquito-borne disease of domestic animals chiefly of eastern and southern Africa that is caused by a bunyavirus (species Rift Valley fever phlebovirus of the genus Phlebovirus), is marked especially by fever, abortion, and death of newborns, and is sometimes transmitted to humans usually in a milder form marked by flu-like symptoms
Keep scrolling for more
Keep scrolling for more
Test Your Vocabulary
Slippery Words Quiz—Changing with the Times
- What is an earlier meaning of nice?

Test your vocabulary with our 10-question quiz!
TAKE THE QUIZ
Anagram puzzles meet word search.
TAKE THE QUIZLove words? Need even more definitions?
Merriam-Webster unabridgedWords at Play
Ask the Editors
Word Games
Slippery Words Quiz—Changing with the Times
Do you know these earlier meanings of words?
Take the quizWords of Snow and Ice Quiz
A selection of words from the chillier parts of t...
Take the quizHow Strong Is Your Vocabulary?
Test your vocabulary with our 10-question quiz!
Take the quizSCRABBLE® Sprint
SCRABBLE® fans, sharpen your skills!
Play the game
Share Rift Valley fever
Time Traveler for Rift Valley fever
The first known use of Rift Valley fever was circa 1931
See more words from the same year