long umbrella; non-folding umbrella
Refers to a traditional straight umbrella with long ribs, as opposed to a folding umbrella (折りたたみ傘).
It's windy today, so a long umbrella is better than a folding one.
長傘 is a full-length, non-folding umbrella, the opposite of the compact, collapsible 折りたたみ傘.
Compound of 長 (naga, 'long') and 傘 (kasa, 'umbrella'), with rendaku voicing of the second element.