Abnormal, atypical and aberrant all mean deviating markedly from the rule or standard of its kind.
Abnormal frequently suggests strangeness and sometimes deformity or monstrosity.
- Tests revealed some abnormal skin cells.
Atypical stresses divergence upward or downward from some established norm.
- The sociable behaviour of lions is considered atypical of the cat family.
Aberrant implies a departure from the usual or natural type.
- Ian's rages and aberrant behavior worsened.