| horizon |
| parallel(adjective, calm, direct, smooth, right) |
| plain(adjective, calm, quiet, smooth, soft) |
| procumbent(adjective, smooth, flat, low, level) |
| tabular(adjective, flat) |
| upright(adjective, smooth, solid, level, true) |
| vertical(adjective, smooth, solid, level, true) |
| aligned(adjective, calm, smooth, flat, plain) |
| balanced(adjective, calm, direct, smooth, right) |
| calm(adjective, smooth, flat, plain, level) |
| erect(verb, adjective, smooth, solid, level) |
| lie |
| linear(adjective, smooth, right, solid, level) |
| lying down(expression, adjective, lying) |
| perpendicular |
| planar(adjective, flat, even) |
| plumb(adjective, direct, smooth, right, flat) |
| steady(adjective, calm, quiet, smooth, right) |
| transverse(adjective, across) |
| undeviating(adjective, quiet, direct, smooth, right) |