The Collaborative International Dictionary of English v.0.48:

Involvement \In*volve"ment\, n.
   The act of involving, or the state of being involved. --Lew
   Wallace.
   [1913 Webster]

WordNet (r) 3.0 (2006):

involvement
    n 1: the act of sharing in the activities of a group; "the
         teacher tried to increase his students' engagement in class
         activities" [syn: engagement, participation,
         involvement, involution] [ant: non-engagement, non-
         involvement, nonparticipation]
    2: a connection of inclusion or containment; "he escaped
       involvement in the accident"; "there was additional
       involvement of the liver and spleen"
    3: a sense of concern with and curiosity about someone or
       something; "an interest in music" [syn: interest,
       involvement]
    4: a usually secretive or illicit sexual relationship [syn:
       affair, affaire, intimacy, liaison, involvement,
       amour]
    5: the condition of sharing in common with others (as fellows or
       partners etc.) [syn: participation, involvement]

Moby Thesaurus II by Grady Ward, 1.0:

155 Moby Thesaurus words for "involvement":
   absorbed attention, absorption, application, arraignability,
   arraignableness, assault, association, assumption, attack, bias,
   blameworthiness, bloody hands, burden, caring, censurability,
   censurableness, censure, chargeability, chord, cincture, circling,
   circumambience, circumambiency, circumcincture, circumflexion,
   circumjacence, circumposition, citation, cochairmanship,
   complexity, complexness, complication, complicity, concentration,
   concern, condominium, containment, contemplation, contribution,
   convolution, copartnership, copartnery, cotenancy, crabbedness,
   criminality, culpability, deep study, deep thought, dirty hands,
   discrimination, echo, embracement, embroilment, empathy,
   encincture, encirclement, enclosure, encompassment, enfoldment,
   engagement, engrossment, enmeshment, entailment, entanglement,
   envelopment, environment, favoritism, fellow feeling, girding,
   girdling, guilt, guiltiness, guilty conscience, having a part,
   identification, immersion, impeachability, impeachableness,
   implication, impugnment, inclination, inclusion, incrimination,
   inculpation, indictability, indictableness, inequality, intentness,
   interagency, intercession, interest, intermediation, interposition,
   intervention, intricacy, intricateness, involution,
   joint chairmanship, joint control, joint ownership, joint tenancy,
   leaning, mediation, meditation, monomania, nepotism, obsession,
   one-sidedness, onus, partaking, parti pris, partiality,
   participation, partisanism, partisanship, partnership, pathos,
   peccancy, perplexity, preference, preferential treatment,
   preoccupation, presumption, profound thought, ramification,
   rapt attention, red-handedness, relating, reprehensibility,
   reproachableness, reprovability, reprovableness, response,
   responsiveness, sharing, single-mindedness, stepping in,
   studiousness, study, submersion, subsumption, subtlety, suffrage,
   surrounding, sympathetic chord, sympathetic response, sympathy,
   tanglement, technicality, undetachment, undispassionateness,
   unneutrality, vibes, vibrations, voting