elusive

(ĭ-lo͞oˈsĭv, -zĭv)

1. Tending to elude capture, perception, comprehension, or memory: “an invisible cabal of conspirators, each more elusive than the archterrorist [himself]” (David Kline).
2. Difficult to define or describe: “Failures are more finely etched in our minds than triumphs, and success is an elusive, if not mythic, goal in our demanding society” (Hugh Drummond).

Related Forms:

• e·luˈsive·ly adverb

• e·luˈsive·ness noun