be (as) dead as a dodo

The "dodo" is a now-extinct bird.

1. To be totally, unquestionably dead. A: "Are you sure the goldfish is dead?" B: "Oh yeah—it's dead as a dodo." I poked that squirrel with a stick and, yeah, it's as dead as a dodo. Any animal unlucky enough to run out into this busy street will be dead as a dodo in a matter of seconds.

2. To be outdated or unpopular Although popular in the 1970s, disco music is as dead as a dodo today. Things like poodle skirts were dead as a dodo when the show Happy Days aired—it was capturing nostalgia for a bygone era, the 1950s. Myspace ruled the early 2000s but was dead as a dodo after Facebook came along.