| safe(adjective, firm, solid, stable, fixed) |
| secure(adjective, firm, solid, stable, fixed) |
| sedate(adjective, firm, sensible, solid, steady) |
| self-possessed(adjective, firm, sensible, solid, steady) |
| sensible(adjective, firm, solid, steady, stable) |
| serene(adjective, firm, sensible, solid, steady) |
| serious-minded(adjective, firm, sensible, solid, steady) |
| set(adjective, firm, solid, stable, fixed) |
| set in stone(expression, adjective, idiom, firm, solid) |
| settled(adjective, firm, sensible, solid, steady) |
| similar(adjective, close, correct, true, realistic) |
| sober(adjective, firm, sensible, solid, steady) |
| solid as a rock(expression, adjective, idiom, firm, solid) |
| sound(adjective, firm, solid, stable, fixed) |
| spirited(adjective, keen, passionate, enthusiastic, fervent) |
| square(adjective, honest, pure, sure, constant) |
| stabile(adjective, firm, solid, stable, fixed) |
| staid(adjective, firm, sensible, solid, steady) |
| stalwart(adjective, reliable, steadfast, loyal, faithful) |
| steady-going(adjective, firm, solid, stable, fixed) |