supposing

1. gerundparticiplepresentpresent participle and gerund of suppose

plural supposings

1. The act of making a supposition.

   She could have joined most comfortably in all their supposings, and suspicions, and doubts, and prognostications, but the honour of the family was too nearly concerned to allow free reins to her tongue.

   1837, The Dublin University Magazine

1. if hypothetically (optionally followed by that)

   Let’s go swimming in the lake. - Supposing there are/were 'gators.

   1 more example

   Supposing our daughter was to marry her sweetheart, and supposing they was to have a son, and supposing he was to grow to man’s estate, and supposing he was to come down to draw cider like as we’re doing, and supposing that there mallet was to fall on his head and kill him, how dreadful it would be!

   2013, Flora Annie Steel, “The Three Sillies”, in English Fairy Tales