KEY: Serious.
SYN: Grave, thoughtful, careful, earnest, solemn, important,weighty.
ANT: Volatile, gay, thoughtless, careless, joking, jocose,insignificant, unimportant, trifling, trivial, light.

• Irreducible
• Irrefragable, [See REFRAGABLE]
• Irrefutable, [See REFRAGABLE]
• Irregular, [See REGULAR]
• Irrelevant, [See RELEVANT]
• Irreligions
• irreligion, [See RELIGION]
• Irremediable, [See REMEDIABLE]
• Irremissible
• Irremovable
• Irreparable, [See REPARABLE]
• Irreprehensible, [See REPREHENSIBLE]
• Irrepressible
• Irreproachable, [See BLAMELESS]
• Irreprovable
• Irresistible, [See RESISTIBLE]
• Irresolute, [See RESOLUTE]
• Irrespective, [See RESPECTIVE]
• Irresponsible
• Irretrievable, [See RETRIEVABLE]
• Irreverence, [See REVERENCE]
• Irreversible, [See REVERSIBLE]
• Irrevocable, [See REVERSIBLE]
• Irrigate
• Irrigation, [See IRRIGATE]