provisional plan; tentative proposal
A plan or proposal that is temporary and subject to change; often used in business, policy, or project contexts.
Please put together a provisional plan by next week's meeting.
This schedule is a tentative proposal, so it may be changed.
案 means 'plan' or 'proposal'; 暫定案 combines it with 暫定 to specify a provisional plan.
Compound of 暫定 (ざんてい, 'provisional, tentative') and 案 (あん, 'plan, proposal').