A pawl, click, or detent for holding or propelling a ratchet wheel, or ratch, etc.
"The mechanic replaced the broken ratchet to restore smooth rotation to the heavy-duty winch."
To cause to become incremented or decremented.
"The software automatically ratchets up the difficulty level every time you complete a stage without taking damage."
Ghetto; unseemly, indecorous.
"The neighborhood was ratchet after the power lines were cut and people started playing music at full volume all night."