[under cover] {adv.} or {adj. phr.} Hidden; concealed. * /The prisoners […]

[under one's thumb] or [under the thumb] {adj.} or {adv. phr.} […]

[under the sun] {adj.} or {adv. phr.} On earth; in the […]

[under wraps] {adv.} or {adj. phr.} Not allowed to be seen […]

[up a stump] {adj. phr.}, {slang} Stumped; blocked; mixed up or […]

[up a tree] {adv.} or {adj. phr.} 1. Hunted or chased […]

[up against it] {adj. phr.}, {informal} Faced with a great difficulty […]

[up for grabs] {adj. phr.}, {informal} Available for anyone to try […]

[up front] (2) {adj.}, {slang}, {informal} Open, sincere, hiding nothing. * […]

[up in arms] {adj. phr.} 1. Equipped with guns or weapons […]