join in a group or effort, participate, take part in / increase / be added to

military power / competitiveness (e.g. in sports) / clout (e.g. of a union)

a fighting force that can be rapidly deployed without needing practice or preparation / (by extension) someone who can be relied on at any time

team

he / distal demonstrative, something far off removed from both speaker and listener: that / boyfriend

distal demonstrative, something far off removed from both speaker and listener: that, yon / particularly, male personal third person pronoun: he / by extension from he: boyfriend

he; boyfriend

a sports team which not run by the company, but by the organization of like-minded people in the local community

(Internet slang) replying instantly; instant reply

teammate