ill-considered

Unwise; foolish: ill-considered actions sure to result in disaster.

adjective

1. Characterized by unthinking boldness and haste: brash, foolhardy, harum-scarum, hasty, headlong, hotheaded, impetuous, improvident, impulsive, incautious, madcap, precipitant, precipitate, rash¹, reckless, slapdash, temerarious, unconsidered. See careful/careless.
2. Not wise: ill-advised, impolitic, imprudent, indiscreet, injudicious, unsound, unwise. See wise/foolish.

The adjective has one meaning:

Meaning #1: not given careful consideration
  Synonyms: ill-judged, improvident, shortsighted