We don't have synonyms for istar yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are star, ishtar and astar.
(n) :
(military, US) Acronym of intelligence, surveillance, target acquisition, and reconnaissance. [(chiefly uncountable) The capacity of mind, especially to understand principles, truths, facts or meanings, acquire knowledge, and apply it to practice; the ability to comprehend and learn; the ability to process sentient experience to generate true beliefs with a justified degree of confidence.]
(n) :
(military, US) Acronym of intelligence, surveillance, target acquisition, and reconnaissance. [(chiefly uncountable) The capacity of mind, especially to understand principles, truths, facts or meanings, acquire knowledge, and apply it to practice; the ability to comprehend and learn; the ability to process sentient experience to generate true beliefs with a justified degree of confidence.]