noun, masculine/ʒa.lɔ̃/plural: jalons
ranging pole, ranging rod; foundation, groundwork; milestone, landmark
“Planter des jalons de distance en distance.” — To plant ranging rods from distance to distance.
1613, jallon, in an unknown sense; 1690 in gardening; uncertain origin, maybe from jalir, ancient form of jaillir (“to spurt out”).