BYOP – Bring Your Own Pen/Pencil. This means the CO didn't leave a pen or pencil in their container or the cache is to small to hold own, therefore you'll need your own to sign the log.
CITO – Cache In Trash Out. CITO is an on-going environmental initiative supported by the worldwide geocaching community. Since 2002, geocachers around the world have been dedicated to improving parks and other cache-friendly places. www.geocaching.com/cito.
CO – Cache Owner
DNF – Did Not Find. This means the geocacher didn't find the cache they were searching for, either because their hunting skills weren't effective enough or the cache may have a problem.
FTF – First to Find - this is what you log when you have been the first to person to find and sign the logbook of the cache.
GCxxxx – All caches have a 'GC' code which makes them unique to search for.
GPSr – Global Position Satellite Receive, basically a GPS device.
GZ – Ground Zero - The exact spot where the cache coordinates take you - eg, "I searched around GZ for a while and eventually found it!"
L: - Left. Means that they left a trade item. Usually logged like this: L: Keychain
LEO – Law Enforcement Officer.
LN – Left Nothing.
LPC – Lamp Post Cache. A common hiding place for caches, particularly in the US. The cache is found by lifting up the 'skirt' of the lamp post. Many people think that this type of cache is over-used!
MKH – Magnetic Key Holder. Often used as a hint to caches that are disguised to look like they conceal a car or house key.
MOC – Members Only Cache. A Members Only Cache is one that’s only available to Premium members of Geocaching.com. Find out more here:http://www.geocaching.com/premium/
P & G – Park and Grab. A cache that's good for quick stop off's on route as they're relatively easy to find and you can park nearby.
PI – Poison Ivy, (beware!)
SBA – Should Be Archived. Log type suggesting that there is a problem with a cache, like it's missing, destroyed or in an area of danger and the administrator needs to archive the listing.
SL – Signed Log. When you find a cache you need to sign the piece of paper inside with your caching username to indicate you found it.
STF – Second To Find. The second person to find the cache and sign it's logbook.
SWAG – Stuff we all get - the toys and tradable items you find in a cache
T: – Took. eg. :T: Keychain L: Golf Ball
TB – Travel Bug. An item with a trackable code on it, see http://www.geocaching.com/track/
TFTC – Thanks For The Cache. Probably the most common acronym, used to say thanks to the cache owner for the hide.
TN – Took Nothing.
TNLN - Took Nothing. Left Nothing.
TNLNSL – Took Nothing, Left Nothing, Signed Log.
TNSL – Took Nothing. Signed Logbook.
TNX4GC – Thanks For The Geocache
TOTT – Tool Of The Trade. This generally indicates that some
type of tool or instrument may be required to retrieve or gain access to a
UPS – Unnatural Pile of Sticks. A nice indicator of where to look!
UPR – Unnatural Pile of Rocks. Tells the finder to look out for some oddly stacked rocks.
URP – Unnatural Rock Pile.
XNSL – Exchanged Nothing, Signed Log.
YAPIDKA – Yet Another Park I Didn’t Know About!
A travel bug
UPR / URP