noun

1. an instrument for determining, or adjusting a surface to, an even horizontal plane: it has a glass tube partly filled with liquid so as to leave an air bubble that moves to the exact center of the tube when the instrument is on an even horizontal plane; often there is another such tube which indicates when the instrument is perpendicular to the horizontal
2. 1. surveyor's level
   2. a measuring of differences in elevation with this instrument
3. 1. a horizontal plane or line; esp., such a plane taken as a basis for the measurement of elevation sea level
   2. the height, or altitude, of such a plane
4. a relatively flat and even area of land or other surface; horizontal area
5. the same horizontal plane to keep the tops of pictures on a level
6. usual or normal position with reference to a certain height water seeks its level
7. position, elevation, or rank considered as one of the planes in a scale of values levels of income
8. a horizontal drift or gallery in a mine
9. the degree of concentration of a substance in a fluid
10. Physics the ratio of a quantity's magnitude to an arbitrarily selected magnitude

Etymology: OFr livel < VL *libellus < L libella, dim. of libra, a balance, level, weight

adjective

1. having no part higher than any other; perfectly flat and even; conforming to the surface of still water
2. conforming to the plane of the horizon; not sloping
3. being of the same height or being in the same plane; even (with)
4. even with the top of the container; not heaping a level teaspoonful
5. 1. equal in importance, rank, degree, etc.
   2. conforming to a specified level or rank high-level talks
   3. equally advanced in development
   4. even or uniform in tone, color, pitch, volume, rate, etc.
6. 1. not having or showing sudden differences or inequalities; well-balanced; equable
   2. not excited or disturbed; calm or steady
7. paid or to be paid in equal amounts over a period of time
8. ☆ Slang honest; straight

adverb

transitive verb leveled -·eled or levelled -·elled, leveling -·el·ing or levelling -·el·ling

1. to make level; specif.,
   1. to make perfectly horizontal by means of a level
   2. to make flat and even
   3. to equalize in height, rank, quality, etc.: often with down or up
   4. to make even in tone, color, pitch, etc.
2. to knock to the ground; demolish; lay low the storm leveled the tree
3. to aim (a gun, etc.) for firing
4. to aim or direct
5. Surveying to determine the differences in altitude in (a plot of ground)

intransitive verb

1. to aim a gun, etc. (at)
2. to bring people or things to an equal rank, condition, etc.: usually with down or up
3. ☆ Slang to be frank and honest (with someone)