KEY: Skulk.
SYN: Hide, sneak, cower, lurk, abscond, slink.
ANT: Appear, issue, parade, show.
=
KEY: Slack.
SYN: Loose, weak, remiss, backward, indiligent, slow, remiss, tardy, lax.
ANT: Tight, tense, strong, active, prompt, diligent, alert, quick, eager.
=
KEY: Slacken.
SYN: Loosen, abate, withhold, remit, languish, flag, moderate.