1. The overground drive for a reciprocating piston pump installed at a borehole (e.g. an oil well)
   - nodding donkey

Encyclopedia: Pump jack

• unsightliness
• unsightly
• unsigned
• unsilenced
• unsimilarity
• unsinkable
• unsized
• unskilful
• unskilfulness
• unskilled
• unskilled person
• unskillful
• unskillfulness
• unslaked lime
• unsleeping
• unsling
• unsloped
• unsmiling
• unsmilingly
• unsmooth
• unsmoothed
• unsnarl
• unsnarled
• unsnarling
• unsociability