fourfold

Short definition from Wiktionary

Adjective

1. 1
   Four times as great; quadruple.
2. 2
   Comprised of four individual members.

Adverb

1. 1
   By a factor of four.

Verb

1. 1
   To increase to four times as much; to multiply by four.

Noun

1. 1
   An algebraic variety of degree 4.