retard
From Longman Dictionary of Contemporary Englishretardre‧tard1 /rɪˈtɑːd $ -ɑːrd/ verb [transitive] formalDELAY to delay the development of something, or to make something happen more slowly than expected SYN slow down Cold weather retards the growth of many plants.→ See Verb tableretardre‧tard2 /ˈriːtɑːd $ -ɑːrd/ noun [countable] spoken not politeSTUPID/NOT INTELLIGENTINSULT an offensive word for a stupid personOrigin retard1 (1400-1500) Latin retardare, from tardus “slow”