This one is for Becca, whose former boyfriend did not believe 'skookum' was a real word.
It has a range of positive meanings. As described in the FAQ from Skookum Tools Ltd. the word can have meanings from 'good,' to 'strong,' 'best,' 'powerful,' 'ultimate,' 'brave' and 'first rate.' Something can beskookum meaning 'really good' or 'right on! 'excellent!', or it can be skookum meaning 'tough' or 'durable'. A skookum burger is either a big or a really tasty hamburger, or both, but when your Mom's food isskookum, it's delicious but also hearty. When you are skookum, you've got a purpose and you're on solid ground, in good health/spirits etc. When used in reference to another person, e.g. "he's skookum", it's used in respect with connotations of trustworthiness, reliability and honesty as well as (possibly but not necessarily) strength and size.
Being called skookum may also mean that someone can be counted on as reliable and hard-working, or is big and strong. In a perhaps slightly less positive vein, skookum house means jail or prison, cf. the English euphemism "the big house" but here meaning "strong house". Skookum tumtum, lit. "strong heart", is generally translated as "brave" or possibly "good-hearted". In the Chinook Jargon, skookum is also used as a verb auxiliary, as in "can" or "to be able". Another compound, though fallen out of use in modern BC English, is skookum lacasset, or strongbox.
A related word skookumchuck means turbulent water or rapids in a stream or river, i.e. "strong water" ("chuck" is Chinook Jargon for "water" or "stream" or "lake"). There are three placenames in British Columbia using this word, one of them for a famous saltwater rapid at the mouth of Sechelt Inlet, the others at rapids on the Lillooet and Columbia Rivers, and also Skookumchuck Rapids Provincial Park on the Shuswap River, just downtream from Mabel Lake in the Monashees region. While the rapid at the mouth of Sechelt Inlet is the Skookumchuck on the coast, the term is used in a general sense for other patches of rough water, typically tidal-exchange rapids at the mouths of other inlets or bays, which are a regular feature of the British Columbia Coast.