Roget's Thesaurus of English Words and Phrases by Peter Mark Roget

139. Irregularity of recurrence — N. irregularity, uncertainty,

unpunctuality; fitfulness &c adj.; capriciousness, ecrhythmus†. Adj. irregular, uncertain, unpunctual, capricious, desultory, fitful, flickering; rambling, rhapsodical; spasmodic; immethodical†, unmethodical, variable. Adv. irregularly &c adj.; by fits and starts &c (discontinuously) 70. SECTION VII. CHANGE