flat

1 flat /ˈflæt/ adjective
flatter; flattest
1 flat
/ˈflæt/
adjective
flatter; flattest
Britannica Dictionary definition of FLAT
1 
: having a smooth, level, or even surface : not having curves or bumps
2 
: having a wide, smooth surface and little thickness
3 
also of a shoe : having a flat heel or no heel
4 
: spread out on or along a surface
5 
: very clear and definite : absolute
◊ In British English the expression and that's flat! is used to stress that a statement or decision is definite and will not be changed.
6 
a  : not changing in amount
b  : not having much business activity
7 
: not having much interest or energy : dull
8 
of a drink : no longer having bubbles
9 
of a tire : not having enough air
10 
music
a  : lower than the true pitch
b  : lower than a specified note by a semitone — compare 1natural 8, 1sharp 13
11 
of lighting conditions : not producing strong shadows
13 
British, of a battery : no longer producing electricity : dead

(as) flat as a pancake

informal
: very flat

— flatly

adverb

— flatness

noun [noncount]
2 flat /ˈflæt/ noun
plural flats
2 flat
/ˈflæt/
noun
plural flats
Britannica Dictionary definition of FLAT
[count]
1 
: a level area of land — usually plural
2 
: a flat part or surface
3 
a  : a musical note that is one semitone lower than a specified note
b  : a written symbol ♭ that is placed before a note to show that it should be played a semitone lower — compare 2natural, 3sharp
4 
US : a shallow box in which young plants are grown
5 
chiefly US : a shoe or slipper that has a flat heel or no heel — usually plural
6 
chiefly British : an apartment typically on one floor — compare apartment
7 
: a tire that does not have enough air
3 flat /ˈflæt/ adverb
3 flat
/ˈflæt/
adverb
Britannica Dictionary definition of FLAT
1 
a  : on or against a flat surface
b  : in the position of someone or something that is lying spread out on the ground or another surface
2 
: exactly or precisely — used to describe something that happens quickly
3 
informal : completely or absolutely
— see also flat out
4 
: below the correct musical pitch — compare 2sharp 2

fall flat

— see 1fall