Lewis & Short

dissĭmŭlo, āvi, ātum, 1, v. a. [dissimilis],

  1. I. to feign that a thing is not that which it is; to dissemble, disguise; to hide, conceal, keep secret (cf.: fingo, simulo, confingo, comminiscor—very freq. and class.).
          1. (α) With acc.: nihil fingam, nihil dissimulem, nihil obtegam, Cic. Att. 1, 18: aliquid (with tegere), Caes. B. C. 1, 19, 2; with obtegere, Suet. Ner. 29; with celare, Ter. And. 1, 1, 105; with occultare, Cic. Off. 1, 30, 105; Caes. B. C. 2, 31, 6; cf. Cic. Rosc. Am. 31, 86: nec, ut emat melius, nec ut vendat, quicquam simulabit aut dissimulabit vir bonus, id. Off. 3, 15; cf. Planc. ap. Cic. Fam. 10, 8, 4: quaedam in actione dissimulata, Quint. 6, 4, 14: consonantium quaedam insequente vocali dissimulatur, is obscured, said of elision in poetry, id. 11, 3, 34: occultam febrem, Hor. Ep. 1, 16, 23; cf. metum, id. C. 2, 20, 17: gaudia, Ov. M. 6, 653: nomen suum, id. Tr. 4, 9, 32: natum cultu, id. M. 13, 163: se, to assume another form, id. ib. 2, 731: deum, i. e. concealing his divinity, id. H. 4, 56; id. F. 5, 504; cf. also pass. with mid. force: dissimulata deam, id. ib. 6, 507; Stat. Silv. 1, 2, 14; and virum veste longa (Achilles), Ov. A. A. 1, 690.
          2. (β) With acc. and inf.: dissimulabam me harum sermoni operam dare, Plaut. Epid. 2, 2, 54; so id. Most. 5, 1, 23; Cic. Att. 8, 1 fin.; Quint. 1, 2, 2; Suet. Caes. 10; 73; Ov. Tr. 1, 7, 5 al.
          3. (γ) With a rel. clause: nec judices, a quo sint moti, dissimulant, Quint. 12, 9, 7; so id. 6 prooem. § 7; Verg. A. 4, 291 al.
          4. * (δ) With quasi: dissimulabo, hos quasi non videam, Plaut. Mil. 4, 2, 2.
            (ε) Absol.: plane ea est; sed quomodo dissimulabat! Plaut. Mil. 2, 5, 53; id. Most. 4, 3, 23; id. Men. 4, 2, 44; 78; Cic. Off. 1, 30, 108; id. Mur. 19, 40 (opp. fateri); Caes. B. C. 1, 19, 1; Hor. S. 1, 9, 66; Ov. H. 17, 151 et saep.: dissimulant, they repress their feelings, Verg. A. 1, 516.
            (ζ) With de: primo fingere alia, dissimulare de conjuratione, etc., Sall. C. 47, 1: de condicione sua, Dig. 40, 13, 4.
  2. * II. To leave unnoticed, to neglect: damnosam curationem, Veg. Vet. 1 prooem. § 5: quod dissimulatum, Amm. 21, 3.
    Hence, dissĭmŭlanter, adv., dissemblingly, clandestinely, secretly: non aperte, nec eodem modo semper, sed varie dissimulanterque conclusis, Cic. Brut. 79, 274; id. Fam. 1, 5, b. fin.; Liv. 40, 23; Suet. Tib. 21 (opp. Palam); Ov. H. 20, 132 al.
    Comp. and sup. do not occur.