Definitions

1. verb

the past tense and second person singular of the verb ‘do’

“Thou didst well to warn me of the danger.”

2. verb (archaic)

a somewhat archaic second person singular of ‘do’ in the past tense

“He didst not forget his promise.”

3. auxiliary verb

used to form the second person singular of the past tense of a main verb

“Thou hadst not eaten anything all day.”