declining, on the decline, decreasing, diminishing, dwindling, shrinking, contracting, tapering off, tailing off, subsiding, slackening, drooping, sinking, ebbing, dimming, fading away, growing faint, lessening, dissolving, petering out, winding down, falling off, attenuating, on the way out, abating, failing, receding, slumping, in a slump, in remission, flagging, atrophying, weakening, giving way, melting away, deteriorating, in a state of deterioration, crumbling, withering, disintegrating, degenerating, evaporating, collapsing, drawing to a close, vanishing, dying out, obsolescent, moribund

informal on one's last legs

rare evanescing