II.Transf., to be faint, weak, drooping, feeble, languid, lazy (not in Cic. or Cæs.): annis corpus jam marcet,Lucr. 3, 946: marcent luxuria, vino, et epulis per totam hiemem confecti,Liv. 23, 45: otio ac desidia corrupti marcebant,Just. 30, 1: pavore,Curt. 4, 13, 18; Vell. 2, 84: si marcet animus, si corpus torpet,Cels. 2, 2: amor,Claud. Laud. Seren. 226: juventa,Nemes. Ecl. 1, 60.—Hence, marcens, entis, P. a., withering, drooping, feeble, wasted away, exhausted, weak, languid, indolent (mostly poet.).
B.Transf.: colla,Stat. Th. 2, 630: guttura,Ov. M. 7, 314: senex marcentibus annis,Sil. 15, 746: visus,Sen. Agam. 788: stomachus,Suet. Calig. 58: terga,Mart. Cap. 6, § 704.—Absol.: tostis marcentem squillis recreabis,Hor. S. 2, 4, 58: Vitellius deses et marcens,Tac. H. 3, 36: pocula,i. e. enfeebling,Stat. S. 4, 6, 56: pax,Tac. G. 36: flamma cupiditatis, Mam. Grat. Act. ad Julian. 17.
Charlton Lewis's shorter dictionary for students: the same scholarship in plain, modern definitions.
marceō —, —, ēre
1 MAR-, to be faint, droop, be feeble, be languid: luxuriā, L.—P. praes.: Potor, H.: pax, Ta.: guttura, O.
Origins
De Vaan derives the verb from Proto-Indo-European *mr̥k-eh₁- (“to be soaked; to be weak”), from a root *merk-. The term theoretically could reflect either the development of *mr̥k- into *mo-, which then may have unrounded to *ma-, or the term may reflect the vocalization of *mr̥k- as *mark-. De Vaan opts for the latter solution, arguing that the forms murcidus imply an o-grade pre-form *mo-, in which case it would be best to assume an original zero-grade pre-form for the verb. If this theory is accepted, then the Proto-Italic intermediary would take the shape *markēō. Schrijver, alternatively, opts to derive the term from earlier Proto-Italic *mork-ē-, from *mr̥k-eh₁-, on the basis that an original stative stem implies that the root likely lacked the o-grade. Regarding the cognates, De Vaan compares Hittite 𒈥𒆠𒅀𒍣 (mar-ki-ya-zi, “to disapprove of, refuse”), Sanskrit मृच् (mṛc, “to injure”), Lithuanian mer̃kti (“to soak”), Middle High German meren (“to dip bread into water or wine”).
The proposed connections with murcus, ἀμόργη (amórgē), Proto-Celtic *mrakis (“malt”) and Lithuanian markýti (“to macerate, to ret”) are problematic for various reasons.