1. The central stone of an arch.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• keystoke,
• cesstode,
• cherystone,
• kystine,
• kerstone,
• kerbston,
• kerbstone,
• kestone,
• keytone,
• jeystone,
• meystone,
• leystone,
• oeystone,
• ieystone,
• kwystone,
• ksystone,
• kdystone,
• krystone,
• k4ystone,
• k3ystone

• causton,
• CSSDNA,
• castdown,
• guesten,
• kostanay,
• kissaten,
• guaiacetin,
• kistna,
• gustin,
• Kyesteine,
• goosedown,
• caston,
• Ghoston,
• casteen,
• costinha,
• caseoiodine,
• gustine,
• CSOTN,
• kosten,
• Gastone,
• gosden,
• gostin,
• GASTINE,
• guesdon,
• kestana,
• CSDDN,
• gastown,
• GACETIN,
• guacetin,
• koston,
• castagna,
• gosdin,
• cassidinae,
• kastan,
• custine,
• Costean,
• kasdan,
• Djudeo-Kasteyano,
• Costin,
• cast on,
• ghost town,
• castagno,
• CCSTN,
• Kiestein,
• Kiestine,
• ghosten,
• costen,
• Kestner,
• kesten,
• kizzuwatna,
• gozitan,
• Cassadina,
• kasten,
• Cassidony,
• Kyestein,
• Kiesteine,
• castano,
• coston,
• WXADWN,
• guston,
• costineÈ™ti,
• costain,
• castanea,
• Kystein,
• kazdin,
• CSTAIN,
• gastonia,
• casdin,
• COSDUNA,
• castine,
• cawston,
• KSDON,
• keston,
• casten,
• costano,
• GSTNE,
• gostiny,
• Gaston,
• goose down,
• cassadine,
• castaigne.

The adjective form of the word "keystone" is "keystoned".

The plural of the "keystone" can be the "keystones".

The singular of the "keystone" can be the "keystone".