When it is a desktop environment. Computers do not have to run windows, some run an alternative called Linux which is Unix for Intel type processors. Linux does not have its own desktop environment, which is how the operating system looks feels and (to a degree) behaves and the users can select between various alternatives such as KDE, Pantheon etc. The most popular of these desktop environments is GNOME.
When it is a tank. One of the most important parts of a vaping e-cigarette is the container that holds the liquid. One of the better known of these is the wismec gnome tank which can be bought separately or as part of a vaping thingy.
When it is an engine. Actually there seem to have been two entirely unconnected gnome engines. The original was first made by the Société Des Moteurs Gnome (the Gnome motor company) around 1905 and was used in many first world war aircraft. Some fifty years later the De Havilland company licensed an engine developed by General electric and developed the turbine Gnome engine (eventually acquired by Rolls Royce)
When it is a poem. A gnomic poem (or gnome) is a short pithy proverb. There is no requirement for this type of ‘poetry’ to rhyme (for example the Exhortation, attributed to Socrates, to “know thyself” is generally considered to be a gnome) but they sometimes do such as “There’s many a slip twixt cup and lip.”
When it is a Lord. Lord Gnome is the fictional owner of private eye who occasionally writes editorials or, more often, makes announcements about one of his companies, which is usually just a way to libel a company that happens to be in the news without getting sued. He is said to be based on a number of newspaper magnates, not least Rupert Murdoch.