Buddha glosses important terms covertly sometimes

Unlike the commentaries, the suttas don't always explicitly say "This word means", "this definition."

But if you pay attention, you realize the Buddha glosses many terms in standard formulas which appear as code words. 

Here's a collection of some important terms being glossed covertly

samādhi sambojjhanga = the 4 jhānas: 

DN 2 in the seven awakening factors section, after passadhi, the 4 jhanas are listed where samādhi sambojjhanga would normally appear.

upekkha-sambojjhanga = realizing the 6 (or 8) higher knowledges while in imperturbable 4th jhāna.

DN 2: happens right after samadhi sambojjhanga, where upekkha would normally be specified

Also compare with 16 suttas in Snp 5, where upekkha (in poetic form as 'pekkha') appears frequently doing vipassana to realize nirvana.

Viveka = judicious-seclusion

MN 139 first jhāna viveka and kāmehi 
(Know how to distinguish different kinds of pleasure.) ‘Sukhavinicchayaṃ jaññā;
(5kg sensuality-cords are to feared, don’t fear 4 jhanas)