Not in keeping with conventional mores or good manners; indecent or immodest
unsuitable to needs or circumstances; inappropriate; inapt
Not properly named; See, for example, improper fraction
Not consistent with established facts; incorrect
Of a complex random variable, correlated with its conjugate
Not according to facts; inaccurate or erroneous
Improper, not according with good standards of behaviour; indecent, indecorous.