Jacom staff - land surveyor
- Jacom staff
- Jaffe
- Jaffe wick
- jag
- jag bolt
- jagged
- jagged line
- jagging
- Jakovlev's instrumental sonde
- jam
- jam nut
- jam of plunger
- jam welding
- Jamaica open spiral auger
- jamb
- Jamin effect
- jammed
- jamming
- jamming of drill string in keyseat
- jamming of drilling shaft
- jamming of drilling tool
- jamming of tool joint thread
- jamproof
- janitor
- Janitor's closet
- Janitorial Services
- jap
- Japan Bank for International Cooperation
- Japan Standard Association:
- Japanese dace
- japanese greenfinch
- japanese snipe
- japanning kettle
- japanning room
- jar
- jar (percussion tool used to deliver heavy blows to objects in hole)
- jar accelerator
- jar block
- jar body
- jar bumper