moonbat
n. A word used by hard-line conservatives to refer to liberals. A fairly silly portmanteau of the words "moon" and "bat," it might be meant to indicate "batting at the moon" as an analogy to attempting to achieve unachievable or unrealistic goals. In general, however, use of this word marks the user himself as the insane, or at the very least, silly, one. 
Oh my god, can you believe those moonbats protesting against warrantless wiretaps of Murrikans? Why can't they just obey everything their president does?!?