Littoral v. Riparian
This is another one from my archive. These are not even remotely synonyms, but are related pairs, and really must be discussed together.
Littoral is a PRIME example of a word that only has one usage and, in fact, is mainly a legal word. In first year property class we learned about riparian and littoral rights (both relating to water), but the first relates to moving water (rivers and streams; Riparian rivers) while the second relates to standing water (lakes and ponds; Littoral lakes). DD doesn't quite make that distinction when defining it, but all the example usages do. So correctly, one would never talk about a farm's littoral irrigation, but rather we can talk about the fact that after my recent sun burn while gardening, I won't be engaging in any littoral sun worshipping activities for the next month.
The definition of riparian is much better than the one given for littoral, which was a little vague on its specificity, and which prompted my legal analysis/discussion. Not that DD has redeemed itself by a slightly better definition which is actually accurate, because it hasn't. This is still a specialized legal word, and would rarely, if ever, be used in a non-legal context, even among erudite speakers. Using this word just makes every lawyer in the room perk up to make sure (a) that it's being used correctly and (b) that you aren't engaging in the unauthorized practice of law. So, enjoy and be careful!