route who's grade hides its difficulty This could be because its undergraded or that it needs a trick move to beat the crux.
To underrate the difficulty of a climb in an effort to either appear cool and confident or to gull others into attempting the route.
The name given to a climb that is significantly more difficult than it's grade suggests.
A bag with sand in it. Attached to the Harness of a light climber to prevent them going airborne when belaying much heavier partners. An under graded Route. Known locally as a "Martyn".
A climb that receives a rating inappropriately low rating for the difficulty.
To mislead someone regarding the difficulty or danger of a route; potentially dangerous
To deliberately underestimate the difficulties of a climb in order to get a climber in over his or her head, often with hilarious or tragic results.
(noun) A route whose grade belies its difficulty. This can be either because it is undergraded, or requires a trick move to overcome the crux. Or it's just more work than it looks. (verb) To point someone at a route that is a sandbag, saying things like "It's only HVS" (unsaid: but requires the skills of an E3 climber). While the grading may get sorted out over time, trick moves tend to keep their grade. Classic example: Verandah Buttress, Stanage (supposedly VD 5b, but harder than 5b!).