Word: besteth
Part of speech: Verb
Syllables: be
steth
Definition: Alternative form of best; thoroughly or completely; fully; often used as a combining form; 
Morphemes:
Affix: best
Language: en
PoS: Verb
Meaning: Had best; get the better of
Affix: -eth
Language: en
PoS: Suffix
Meaning: Used to form the third-person singular present indicative of verbs.