The rare daily word game sweeping the globe. Find what's hidden in plain sight.
SERUM
Definition of SERUM
noun
Ellipsis of blood serum.
Wiktionary · CC BY-SA
Where it comes from
From Latin serum (“whey”). Cognates include French sérum, Spanish suero, Italian siere, siero, Portuguese soro. Doublet of suero.
Etymology via Wiktionary (CC BY-SA).
Word DNA
Line of descent
- Latin
- English
One recorded step before English.
Deepest traced root
1st
of 59 source languages in OUTLIER
30.6%
of traced words share this origin (25,378)
branch · 30.6% of traced words
How it is built
Same root, SERUM · 3 relatives in the game
Its etymology also names French, Italian, Portuguese, Spanish.
OUTLIER scores every word on how unusual it is, and that number is not published. Working it out at the board is the game.
SERUM in OUTLIER
Players have found it on 29 boards so far. 34 players have found it across Outlier's history.
It first turned up on Day 21, 10 June 2026. The most recent board was Day 158, 25 October 2026. Nobody has seen it on a board for 10 days.
First ever to find it
on Day 21, 10 June 2026 - before anyone else in Outlier's history. See the Pioneers
Built from these letters
SERUM starts with S and ends with M. Sorted, its letters read EMRSU - the shape to hunt for when the grid is scrambled. No letter is used twice, which makes it an isogram.
Same letters, different word
4 other words use exactly these letters. Worth knowing at the board: an anagram fits a grid the same way.
Also seen on Day 21
Could you have found SERUM?
OUTLIER is a daily word game. One grid, the same grid for everybody, and the words nobody else spots are the ones that pay. This word was on Day 21 - and most players walked straight past it.
Play today's OUTLIER