Indefensible and untenable describe views, arguments, or stances that are not capable of being defended or maintained against criticism. When indefensible is used of actions or behavior, however, it implies that they are morally unjustifiable, or inexcusable. Untenable, rooted ultimately in the Latin verb for “to hold,” suggests inability to be maintained, supported, or defended. An untenable argument or position on an issue will not hold up, perhaps because they are easily proved to be flawed or unsound, but not only for that reason. New developments in the world may make a position untenable. The common recent usage, untenable situation, means a situation that is incapable of being sustained, borne, or coped with, which is nudging the word further away from being synonymous with indefensible.
In the context of writing and speaking, expand and elaborate (both usually followed by “on”) refer to saying more about an idea, topic, or statement so as to address it more fully or convincingly. Expand on is a slightly looser term–if you say something interesting in class and the professor asks you to expand on that idea, she wants you to say more, but “more” could mean a lot of things–from explaining the idea in more detail to expressing more thoughts about it at large. Elaborate on is used very similarly, although strictly it refers to expanding something that is by implication underdeveloped by adding details to support or develop an idea, point, statement, theme, or argument. Officials are forever declining to elaborate on the terse comments they give to the press, who just want the scoop.
rSearch and rummage refer to carefully or thoroughly looking for something missing or lost. To search is to carefully move through or look through a place or space to find a person or thing: We searched the amusement park for the missing child; He searched her desk for the letter. Rummage has a narrower range of application and specifies the manner of searching. If you rummage through a suitcase, you move things around or turn them over in order to search. Usually what is rummaged through is a receptacle or a space where things are very close together–a purse, a trash can, cupboards, drawers, an attic, or a wardrobe. If there is only a carton of milk and a package of tofu dogs in the refrigerator, you can’t really rummage through that.