WordNet sense 1 (a relative position or degree of value in a graded group):

grade, tier, tier

WordNet sense 2 (a specific identifiable position in a continuum or series or especially in a process):

degree, point, stage

WordNet sense 3 (an abstract place usually conceived as having depth):

layer, stratum

WordNet sense 4 (indicator that establishes the horizontal when a bubble is centered in a tube of liquid):

spirit level

WordNet sense 5 (a flat surface at right angles to a plumb line):

horizontal surface

WordNet sense 6 (a structure consisting of a room or set of rooms at a single position along a vertical scale):

floor, storey, story

WordNet sense 7 (not showing abrupt variations):

unwavering

WordNet sense 8 (not subject to change or variation especially in behavior):

steady

WordNet sense 9 (tear down so as to make flat with the ground):

dismantle, raze, rase, take down, tear down, pull down

WordNet sense 10 (make level or straight):

flush, even out

WordNet sense 11 (parallel to or in the plane of the horizon or a base line):

horizontal

WordNet sense 12 (direct into a position for use):

charge

WordNet sense 13 (having a surface without slope, tilt in which no part is higher or lower than another):

flat, plane

WordNet sense 14 (being level or straight or regular and without variation as e.g. in shape or texture; or being in the same plane or at the same height as something else (i.e. even with)):

even

WordNet sense 15 (of the score in a contest):

tied

WordNet sense 16 (well matched; having the same quantity, value, or measure as another):

equal

WordNet sense 17 (become level or even):

level off