| ENDOFTHELINE | Point beyond which it is useless or impossible to proceed (3,2,3,4) |
| STYMIE | Situation from which it is almost impossible to proceed (6) |
| ENDOFTHEROAD | Point beyond which survival is impossible (3,2,3,4) |
| ASCLEARASMUD | Sarcastic oxymoron meaning difficult or impossible to understand (2,5,2,3) |
| INACCESSIBLE | Difficult or impossible to reach (12) |
| IMPONDERABLE | Difficult or impossible to assess (12) |
| MONTECARLOMETHOD | Use of repeated random sampling to estimate a numerical result which is difficult or impossible to calculate |
| EVEORIZON | Point beyond which light cannot escape from a black hole |
| THEENDOFTHEROAD | Point beyond which one can no longer continue |
| TRANSPARENT | Easy to see or impossible to see |
| MYSTERY | Something that is difficult or impossible to understand (7) |
| MYSTERIOUS | Difficult or impossible to understand, explain, or identify (10) |
| FELINEINTHESAND | Point beyond which the cat just won't go? |
| INCREDIBLE | Amazing or impossible to believe (10) |
| FUTILE | If it's bad fuel, it is useless (6) |
| TREASONOUS | Time to be rational, wanting nothing useless or liable to harm the homeland |
| NOHELP | New parking with bad hole in it is useless (2,4) |
| TREELINE | The edge of a habitat beyond which, due to cold, altitude, aridity, exposure to wind or other cause, only shrubs or smaller plants can grow (4-4) |
| LIMIT | Impose bounds beyond which it's impossible to go (5) |
| BLOCKAGE | An obstruction that makes movement or flow difficult or impossible (8) |
