manna lichen

from the GNU version of the Collaborative International Dictionary of English.

• noun Any of several Old World semicrustaceous or shrubby lecanoras that roll up and are blown about over African and Arabian deserts and used as food by people and animals; same as manna{2}.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun any of several Old World partially crustaceous or shrubby lecanoras that roll up and are blown about over African and Arabian deserts and used as food by people and animals