Steep, abrupt, precipitous, sheer mean having an incline approaching the perpendicular.
The words are here arranged in ascending order of degree of perpendicularity.
Steep implies so sharp a slope or pitch that ascent or descent is difficult.
Abrupt adds to steep the suggestion of a sharper pitch or angle of ascent or descent and usually of a sudden break in a level.
Precipitous suggests extreme steepness and an abruptness like that of a precipice.
Sheer implies precipitousness approaching the perpendicular and showing no break in its line.