adjective
1.
moving about aimlessly or irregularly without a fixed course
an erratic breeze barely stirred the leaves of the tree
Synonyms: devious, errant, stray, wandering
Related Word: curving, meandering, roundabout, winding; shifting, undirected
Contrasted words: fixed, stable, unmoving; active, animated, brisk, lively, sprightly
Antonyms: static
2.
Synonyms: uncertain 1, capricious, chancy, dicey, fluctuant, iffy, incalculable, unpredictable, whimsical
Related Word: doubtful, dubious
Antonyms: stable
3.
Synonyms: arbitrary 1, capricious, freakish, vagarious, wayward, whimsical, whimsied
Related Word: changeable, inconsistent, inconstant, unpredictable, variable; mercurial, unstable, volatile
Contrasted words: consistent, conventional, predictable, stable
4.
Synonyms: strange 4, bizarre, eccentric, idiosyncratic, oddball, peculiar, queer, singular, unusual, weird
Related Word: anomalous, irregular, unnatural
Contrasted words: natural, normal, regular, typical; customary, usual