I is for...Irony and Ignorance. These are two of my biggest pet peeve words and are the pet peeves of many other English enthusiasts and perfectionists. If you don't know the definitions of these words, then you just might be using them incorrectly. It would be in your best interest to learn the definitions, however, so that you can use them correctly in your speech and in your writing.
Irony is defined by Merriam-Webster as "a) the use of words to express something other than and especially the opposite of the literal meaning; b) a usually humorous or sardonic literary style or form characterized by irony; c) an ironic expression or utterance." For example, if you drive past a fender-bender at an intersection, making fun of the distracted drivers, then get into a fender-bender yourself, that is ironic. If you need help distinguishing between what is ironic and what is not, try posting your dilemma here: http://www.isitironic.com/.
Ignorance is defined as a "lack of knowledge." If someone intentionally cuts you in line, they are not ignorant (at least, you can't come to that conclusion from that one incident). They might be stupid or rude, but they are not ignorant. If, however, someone admits that they do not know anything about robins, then they could be considered ignorant about robins. This doesn't mean that they are stupid, it just means that they have not had any experiences with robins.
If you have any questions about the usage of these two words, please leave me a comment and I will be more than happy to help you out!