1 B1 informal
Of a liquid or mixture: to form unwanted lumps or clumps, becoming uneven in texture.
"The gravy will lump up if you don't keep stirring it over the heat."
inseparable
lump up
B2 informal separable transitive/intransitive
To form into lumps or lumpy masses; or to cause something to become lumpy or uneven.
In plain English
To get lumpy or bumpy, or to make something get lumpy, like sauce that hasn't been stirred properly.
What does "lump up" mean?
2 meanings, ordered from most common to least. Color-coded by CEFR level.
2 B2 informal
Of a surface, muscle, or material: to develop raised bumps or uneven protrusions.
"The old plaster had started to lump up in places, making the wall look terrible."
inseparable
Literal vs figurative
Words literally mean
'Lump' means a raised, rounded mass; 'up' signals the formation or increase of such masses. Largely transparent.
Actually means
To get lumpy or bumpy, or to make something get lumpy, like sauce that hasn't been stirred properly.
Usage tip
Relatively informal and uncommon. Used in cooking (sauces lumping up), physical descriptions (muscles, surfaces), or figuratively to describe things becoming messy or uneven. Less common than simply using 'lump' as a verb on its own.
Words that pair with "lump up"
Natural word combinations native speakers use most often.
sauce gravy muscles surface mixture plaster
How to conjugate "lump up"
The five tense forms you'll use most often.
Base
lump up
I/you/we/they
3rd person
lumps up
he/she/it
Past simple
lumped up
yesterday
Past participle
lumped up
have + pp
-ing form
lumping up
continuous
Hear "lump up" in the wild
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