sav ‧ ant /ˈsæv ə nt $ səˈvɑːnt, sæ-/ BrE AmE noun [countable] formal
[ Date: 1700-1800 ; Language: French ; Origin: present participle of savoir 'to know' ]
1 . someone who knows a lot about a subject
2 . someone who has mental problems and may have lower intelligence than average, but who can do one thing very well, such as adding numbers very quickly