(1) A hoodoo is a finger of rock or hard soil that pokes upward from an arid landscape. Hoodoos range from roughly five to 150 feet (1.5 to 45 meters) in height.
They form when relatively soft rock, topped by harder rock, erodes away, leaving behind the typical columnar formation. Usually the softer under-rock has a sedimentary or volcanic origin. The hard stuff on top forms a "cap rock", which is like a protective, stony cap on top of the hoodoo.
Hoodoos mainly form in desert or hot, near-desert areas such as the U.S. Southwest's Colorado Plateau and the Badlands regions of the Northern Great Plains.
Two weathering processes create hoodoos: frost wedging and rainfall.
Frost wedging happens when liquid water seeps into cracks and freezes, usually at night. Freezing expands water by about 10%, prying open cracks and splitting rock.
Liquid water washes away loose soil and loose stone, and is also slightly acidic, so it can eat away at certain types of stone.
Different kinds of minerals within different rock types in hoodoos are responsible for horizontal bands of varying colors.
The average hoodoo in Bryce Canyon (known for its hoodoo gardens) erodes at the rate of two to four feet (0.5 to 1.5 meters) per 100 years.
(2) A goblin, tent rock, fairy chimney, earth pyramid.
(3) A jinx (originally from baseball slang). A charm. A spell.
The jinx [is] that peculiar hoodoo which affects, at times, a man, at other times a whole team. Let a man begin to think that there is a jinx about, and he is done for for the time being. (Technical World Magazine, 1911)
Don't try no voodoo near them hoodoo. They could fall on your head an give you a good jinxin' fer sure, Ed.