un·due /ˌən-'dü, -'dyü/ adj1: not due: not yet payablean undue bill2: exceeding or violating propriety or fitnesswould impose undue hardship on the debtorssuch a requirement would place an undue burden on employers
Merriam-Webster’s Dictionary of Law. Merriam-Webster. 1996.
disproportionate, exceeding propriety, excessive, exorbitant, extravagant, extreme, ill-advised, immoderate, immodicus, improper, inappropriate, indecorous, inordinate, needless, nimius, objectionable, out of bounds, outrageous, overmuch, profuse, superfluous, unbecoming, unbefitting, uncalled-for, undeserved, unfit, unjustified, unmerited, unnecessary, unneeded, unreasonable, unseemly, unsuitable, unwarranted
associated concepts: undue influence
(not owing) adjective
not mature, not yet due, not yet payable, premature, unowed, unseasonable, untimely
disproportionate, drastic, excess, excessive, exorbitant, extreme (exaggerated), gratuitous (unwarranted), improper, inadmissible, inapposite, inappropriate, inapt, inept (inappropriate), inordinate, outrageous, prohibitive (costly), redundant, unauthorized, unfit, unreasonable, unseemly, unwarranted, usurious, wrongful
Burton's Legal Thesaurus. William C. Burton. 2006
adj.Improper; unwarranted; exceeding what is necessary.
The Essential Law Dictionary. — Sphinx Publishing, An imprint of Sourcebooks, Inc. Amy Hackney Blackwell. 2008.