We don't have synonyms for supersub yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are superb, superbug and superset.
(n) :
(sports) A substitute player who significantly contributes to a team's success.
(n) :
(cricket) In non-standard cricketing rules, a substitute player who is able to come on and replace any player at any point during the game, and to take over the other player's batting and bowling duties.
(n) :
A particularly well-equipped and powerful submarine (underwater vehicle).
(n) :
(sports) A substitute player who significantly contributes to a team's success.
(n) :
(cricket) In non-standard cricketing rules, a substitute player who is able to come on and replace any player at any point during the game, and to take over the other player's batting and bowling duties.
(n) :
A particularly well-equipped and powerful submarine (underwater vehicle).