The Collaborative International Dictionary of English v.0.48:

Plugging \Plug"ging\, n.
   1. The act of stopping with a plug.
      [1913 Webster]

   2. The material of which a plug or stopple is made.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Plug \Plug\, v. t. [imp. & p. p. Plugged; p. pr. & vb. n.
   Plugging.]
   To stop with a plug; to make tight by stopping a hole.
   [1913 Webster]

   2. To briefly publicize or advertise, especially during a
      public event not specifically intended for advertising
      purposes; as, during the interview he plugged his new
      book.

   Syn: put in a plug for.
        [PJC]

Moby Thesaurus II by Grady Ward, 1.0:

132 Moby Thesaurus words for "plugging":
   application, assiduity, assiduous, assiduousness, bulldog tenacity,
   concentration, constancy, constant, continuing, diligence,
   diligent, dogged, dogged perseverance, doggedness, donkeywork,
   drudge, drudgery, drudging, endurance, enduring, engrossment,
   faithful, fidelity, grind, grinding, grubbing, hardworking,
   immutable, inalterable, indefatigability, indefatigable,
   indomitable, industrious, industriousness, industry, insistence,
   insistency, insistent, invincible, labor, laboring, lasting, loyal,
   loyalty, moil, never-tiring, obstinacy, obstinate, patience,
   patience of Job, patient, patient as Job, pegging, permanence,
   permanent, perseverance, perseverant, persevering, persistence,
   persistency, persistent, persisting, pertinacious,
   pertinaciousness, pertinacity, plodding, preoccupation,
   preoccupied, rapt, relentless, relentlessness, resolute,
   resolution, sedulity, sedulous, sedulousness, single-minded,
   single-mindedness, singleness of purpose, slavery, slaving,
   sleepless, slogging, stability, stable, stamina, staying power,
   steadfast, steadfastness, steadiness, steady, stick-to-itiveness,
   straining, striving, struggling, stubborn, stubbornness, sweating,
   tenacious, tenaciousness, tenacity, tireless, tirelessness, toil,
   toiling, unabating, unconquerable, undaunted, undiscouraged,
   undrooping, unfailing, unfaltering, unflagging, unflinching,
   unintermitting, uninterrupted, unnodding, unrelaxing, unrelenting,
   unremitting, unremittingness, unsleeping, unswerving,
   unswerving attention, untiring, unwavering, unwearied, unwearying,
   unwinking, utterly attentive, weariless, working